CZ6694A3 - High-effective ventilator with adaptable noise removal - Google Patents

Abstract

This invention relates to a new type of compact high efficiency fan utilizing microphones (74, 75), a loudspeaker (69, 70) and a totally adaptive noise cancellation controller (73) whereby the design of the fan eliminates broadband noise and the controller reduces the remaining tonal component thus producing a high efficient silent fan.

Description

Technical field

The invention relates to an increase in the efficiency of both centrifugal axle fan tolls while at the same time eliminating the increased noise caused by an increase in their efficiency.

By way of example, a typical blower or centrifugal fan is shown here with reference to Figure 13.

The geometry of the centrifugal fan casing is characterized by an expansion angle,, the developed length 5 5 and the width of the casing Wfo. The expansion angle defines the degree of expansion of the spiral fan housing. As is known, two types of expansion are used; either linear or exponential. For linear expansion, the radius of curvature of the helical casing is mathematically described by the relation

where r is the radius at a certain circumferential position, it is apparent that the radius of curvature of the spiral increases linearly depending on the circumferential position y. The mathematical description of the exponential extension is r = r ^ exp

The developed length r defines the length along which the fan housing extends. The smallest distance between the impeller and the blower casing causes the casing to close and is therefore called the clearance clearance and is designated CC. The conclusion contributes to directing the flow from the impeller to the exhaust of the fan housing. The breech geometry is typically characterized by the breech radius r _c .

The tonal noise component of the centrifugal fan is generated in the region of the enclosure end by the interaction of a non-uniform flow leaving the impeller. This process causes large pressure losses at the ventilator end, which in turn translates into a transverse blade sound, BPF (BPF = Z.N, where Z is the number of impeller blades and N is the impeller rotational speed) and higher harmonics. It will be appreciated that the velocity profile of the ventilator discharge is equalized as the distance between the impeller blades and the ventilator end is increased. The increased clearance thus reduces the pressure losses in the breech area and is consequently a suitable way to reduce the tonal noise components of the centrifugal fan, but reduces the efficiency of the fan and increases random broadband noise.

Another design parameter that affects the tonal blower noise is the radius of curvature r. However, it has been found that the effect of this parameter is less important than the closing clearance CC. However, it has also been shown that a noise reduction of up to 6 dB can be achieved by increasing the breech radius r without affecting the performance of the gripper or its efficiency.

A conventional fan is characterized in that the end of the breech is parallel to the impeller blades. Such an arrangement causes pressure losses that are in phase along the entire length of the breech and thus increase the emission of noise. The deflection of either the impeller blades or the end of the breech or both _z relative to the impeller axis _z causes a gradual phase shift of the loss pressures acting along the breech length, resulting in a certain reduction in the radiated sound.

By deploying the blades irregularly on the impeller, the sound energy generated by the orbiting blades may be spread over a wider sound band. This may be desirable from a subjective point of view, but the overall sound power generated usually remains unchanged. It has been shown that, under certain operating conditions, irregularly spaced vanes can cause out-of-band tones having a higher level than the original tone caused by the orbiting vanes.

Neise and Koopmann successfully reduced the tone caused by the orbiting blades by using an acoustic resonator at the end of the fan. The resonator was formed from a series of perforated plates with the same curvature as the original enclosure to maintain the original fan housing geometry. The resonator could be tuned by changing its length through a movable fork. By using a resonator, the tone could be reduced by up to 29 dB, which means lowering the overall sound level to 7 dB (A). The aerodynamic design of the blower was not affected by the addition of the resonator to its housing. Such a system operates at a single fan speed.

Relatively few fans have explicitly addressed broadband noise reduction. Neis discloses Petrov transition webs in his application. Fine mesh, located at the leading edge of the blade (ie around the inner circumference of the impeller), causes small turbulent flow around the net. As a result of the blade boundary, a turbulent layer is formed and the point of current dissipation is accordingly shifted towards the trailing edge of the blade. A second transition network located around the outer periphery of the impeller aligns the output velocity profile and is therefore likely to further reduce turbulence in the vortices behind the vanes and may therefore cause noise reduction. As has been observed, the main disadvantage of the overrunning nets is the reduced efficiency of the fan, especially with impellers having forward curved blades.

The most comprehensive experimental investigation of the effect of design parameters on the centrifugal regulator noise has been conducted by Morinushie to date. His finding was that there were five (5) important design parameters related to noise generation and aerodynamic design of the centrifugal regulator characterizing the impeller with blades forward curved and having an outer diameter of 0.18 m. made up of:

1) the ratio of the width to the inner diameter of the impeller-57

2) axial inlet clearance CL ·

3) blade pitch angle (defined as the angle between the chord of the blade and the radial line extending from the impeller axis;

4) ratio of blade height to chord length

5) Spiral extension angle.

BACKGROUND OF THE INVENTION

The present invention represents an important step forward from the initial attempts to construct silent fans and their blades, which are used to move eg air.

Passive techniques such as various silencers, insulating fabrics and different walls were used to absorb noise in the initial experiments.

While such measures reduced only some sounds, most of them remained and thus the question arose as to how to remove them. To reduce this noise, designers simply converted it to broadband at the cost of reducing fan efficiency.

Only recently, another, third means of active noise cancellation has been used. This method utilizes linear flow techniques or channel solutions. The disadvantages of such a solution are that the pipe, respectively. the channel must be extremely long and the microphones themselves must be in the air stream.

The present invention overcomes all previous solutions. The system of the present invention reduces the random noise component by a better fan design. This system also eliminates tonal noise using an adaptable active control unit. The advantages of the present invention are as follows. There is no need for a long channel, no need for microphones to be placed directly in the airflow, which reduces the cost of microphone installation, the fans are essentially completely silent, and are highly efficient, thus reducing electrical power requirements.

It is most preferred that the fan operates as close as possible to the maximum efficiency range. A preferred guide to ensure such a condition is a parameter known as a specific velocity, which binds all variables that affect the choice of any air blowing device

Ql / 2n

P _s ^3/4 where N _g = specific speed

Q = flow rate in Cfm n = rotational speed in rpm p = statistical pressure given by height in inches of water column, s

The meaning of the specific velocity is derived from the fact that for any fan design there is an achievable efficiency value for a given specific velocity value regardless of the fan size or rotational velocity. The type of application of the ventilator determines the specific speed at which the ventilator must operate, and the optimum choice of ventilator is when it has high efficiency at the specific speed required by the application.

FIG. 14 shows the ranges of suitable specific speeds to which the corresponding products are assigned. As shown in the figure, forward curved blades can be used in the range of specific speeds from 7000 to 55000 with best results in the range of 20000 to 35000, mixed flow impellers can be used in the range of 20000 to 70000, preferably in the range of 30000 to 55000, while propeller fans can operate in the range of 90000 to 215000, but most effectively in the range of 100000 to 150000.

Typically, the fan operator has some freedom in selecting a specific velocity as a selection criterion since the numerical value of the specific velocity for a given embodiment is proportional to the rotational velocity. By correctly selecting the rotational speed for the desired device, a specific speed can be achieved so that it falls within the range of the high efficiency area for the desired type of fan. An approximation to this is particularly easy to achieve with belt driven fans. When directly driven by an electric motor, achieving the desired rotational speed values is more limited.

Where high efficiencies are required in the specific speed range between mixed flow fans and axial fans, some manufacturers may supply a custom designed fan; for a speed range below the standard fans, fans with a specific speed of 3000 can be supplied. The fans can also be supplied for specific speeds as low as 1000.

14, the fan generally operates _f to reduce the noise level with a specific velocity according to the slope of the line, delimiting a diamond-shaped region from 200 to the top of the region at a specific velocity 300 where higher efficiency is achieved. If the selection of the specific velocity is outside of the indicated slopes, the noise waveforms change from tonal to random.

The prior art fans represented a trade-off between efficiency and acceptable noise. Often increasing the efficiency of fans requires less play between the impeller and the fan housing, while reducing the broadband noise level results in a stronger tonal sound. However, these tones are judged to be less acceptable than broadband _# random noise. Therefore, the efficiencies have been reduced to achieve acceptable broadband random noise for the fan. However, the broadband noise level is higher than the corresponding fan efficiency.

Bartenwerfer et.al. ^ in the article Noise Reduction in Centrifugal Fans with an Acoustically Designed Enclosure. Nois Control Engineering, May-June 1977, Vol. 8, No. 5, pages 100 to 107, described a method of reducing the sound level over the entire area by means of an acoustically designed fan housing. However, this solution is unacceptable in some environments and transmits significant tonal noises.

Neise and Koopmann, in the Journal of Vibration an Acoustics, describe the use of tuned resonators located at the end of a centrifugal fan to create a secondary source of partially disruptive tone generated by the passage of the blades. In addition, they disclose an electrical system that generates a disturbing sound by filtering a signal that is varied with time from the fan and manually adjusting the phase of the aplitude of each frequency component of the disturbing signal. The electronic system utilized expensive laboratory test equipment and required manual adjustment made it useless in corresponding applications. Neither tuned resonators nor the electronic system adapt to changes in the frequency phase or amplitude of the noise generated by the fan. In addition, simply added tonal noise centrifugation to an imperfect fan will not increase fan efficiency or reduce broadband random noise. Neise goes further in the same direction in the Review of Methods for Noise Reduction in Centrifugal Fans, published in the Journal of Engineering for Industry 104, pp. 151-161, 1982.

Neise in the UK. No. 2,117,646 describes the application of its technology, thereby attempting to overcome the problem of constant forced tuning of the resonator length. It uses a system in which the sound source is influenced by frequency changes corresponding to the impeller speed. Phases the audio source opposite to the sound that it wishes to be eliminated and states that the noises are at least partially eliminated. To achieve partial silence, it uses an adjustable phase shift circuit using an audio transducer. He used a microphone on the side of the loudspeaker to activate the counter-phase sound. In the latest wiring, it uses a phase shift circuit that is adjusted so that amplitude is used to change the sound level with the opposite phase.

The prior art adaptive noise suppression methods applied to eliminate fan noise use a channel in which a noise detecting sensor is installed upstream of the blowing air, and a sound generating unit to remove the fan's own noise is placed downstream.

Chaplin in Anti-noise-the Essex Breakthrough Chartered Mechanical Engineer, pp. 41-48, 1983, together with GLWarmak in U.S. Pat. No. 4,473,906 and Ericksson in Active Sound System with On-Line Speaker, Detecting Deviations and feedback from U.S. Patent No. 4,677,676 disclose such methods. However, these methods require a channel length such that they are unsuitable for small installations, further require higher costs and there is a danger of installing the sensor in a place with the possibility of turbulent air flow. They eliminate noise in one direction only, often on the outlet side. To eliminate noise at the inlet side of the fan, a second installation must be used. However, this makes it difficult to interact.

Hill, in U.S. Patent No. 5,010,516, discloses an active acoustic system for attenuating fan noise caused by blade rotation utilizing a rotational velocity derived sinusoidal signal generated by an accelerometer coupled to the fan and utilized for an adaptive filter that controls the loudspeaker generating noise suppression.

Quinlan, in Proceedings of Inter-noise 89, p. 479482, entitled "Active Effect of Noise from Small Axial Fans," described noise reduction in axial fans using a device producing an electromagnetic secondary sound, but this method does not adapt to changes in noise and does not improve efficiency fan.

SUMMARY OF THE INVENTION

The object of the present invention are silent fans using a fully adaptable control unit.

Another feature of the invention is both a quiet-running fan and at the same time achieving a higher efficiency of the fan.

Another object of the invention is to achieve lower broadband noise in a fan with a more efficient design and electronic removal of the tonal noise component.

The following object of the invention is to reduce the closing clearance of centrifugal fans and to subsequently sense and electronically remove increased noise.

Yet another object of the invention is a rapid adaptive system for monitoring changes in frequency, phase and amplitude of noise emitted by a more efficient fan due to a reduction in its clearance. It is also a feature of the invention to eliminate the need to use resonators in silent fans.

It is a further object of the invention to reduce all dimensions of the fan and its housing.

Another object of the invention is to reduce the electrical power input of the fan.

Finally, another object of the invention is to reduce the cost of microphones required to operate the system.

Description of the invention

The present invention provides a more efficient and quieter fan, which is achieved by combining a highly efficient fan design with active adaptive tonal noise interference. Fan efficiency is improved by reducing clearance at the fan, such as between the impeller and the fan housing, between the impeller blades and the fan enclosure. Generally, reducing these clearances leads to an increase in tonal sound at multiple frequencies of rotating blades. These tones are an active adaptive removal method that responds automatically to changes in the frequency, phase, and amplitude of the tonal components of that noise. Moreover, the method according to the invention does not need the use of channels. as in active noise removal systems of the prior art. The solution of the present invention eliminates noise at both the inlet and outlet sides of the fan.

It is well known in the art that active noise removal in a free space is critically dependent on the wavelength of the sound to be eliminated, as well as the position of the sound removal sound sources. For example, a simple two-position model shows that two sources must be located within approximately 1/10 of the wavelength to reduce the noise amplitude by 6 dB. Further reducing the amplitude even requires a smaller pitch.

However, using an even relatively short channel, the pitch between the two sound sources can be increased such that the shortest wavelength that can be suppressed is approximately equal to twice the largest dimension of the rectangular channel or 1.7 times the diameter of the circular channel. For example, noise from a small fan blowing into a channel with n

the largest dimension 6 could be removed to approximately 1100 Hz.

At present, the most efficient application of the device for active control of random noise is its use in linear systems, ie where the noise propagates through the channel and is therefore more effectively sensed, analyzed and disturbed.

Generally, the input microphone may be located near the noise source and the interfering loudspeaker far enough downstream of the blower air to give the control unit time to determine the necessary frequency, phase and amplitude of the sound. An additional microphone may be adjacent to the fan, or be positioned upstream to sense residual noise, the information of which is then sent to the control unit, which makes appropriate adjustments for any deviation.

For years, experiments with direct transducers have been carried out so that disturbing sound waves do not interrupt the input microphone signals. This work was difficult, complicated and never led to an acceptable solution. Another concept was to use a flip-flop or synch pulse. This solution will work for repetitive tones, but will probably not provide the controller with the right information to analyze random broadband non-repeating propagating sound.

Other control units have been described in many publications and at various symposiums. The way to create an electronic replacement for the acoustic wave created in the fan channel is shown in Figure 2. The regulated system is in fact a propagating sound wave along with a pattern of a comprehensive range of transmission functions that allow the control unit to evaluate how the propagating sound waves change channel. The control unit comprises a high-speed digital processor and consists of one or more adaptive filters including one that replaces the acoustic feedback. It should be noted that the system can achieve universal noise elimination (along the entire channel cross section) with only plane waves. Testing in the laboratory and in practice suggests that higher order modes will still be present in the single-channel system when the microphone is misaligned, and therefore the control unit only interrupts a special phase.

Obviously, the control unit must ensure:

Response to changes in the noise source (change in amplitude and frequency of tonal sound); and

2) response to system changes (temperature, flow rate, transmission characteristics, equipment errors).

The length of the noise elimination system shall be:

(1) the length of the microphone probe and its location outside the most turbulent outlet area; and

2) the distance between the microphone and the loudspeaker, which provides the control unit with the required time delay needed to anaphore the propagating sound.

Centrifugal fans with radial blades are used for material handling. These paddle fans create a very strong tone, corresponding to the blade rotation frequency, as well as higher harmonics, very similar to those of a vacuum pump.

In this fan application, the material flows into the channels, then into the active noise cancellation system component, removes the tones up to the frequency of tones occurring at the fan end. An active system has the advantage over conventional silencers in that it cannot clog the material, eg after a few hours of operation, as it could happen with conventional silencers.

A very important condition when using an active sound control unit is knowledge of the nature of the noise. Conventional absorber attenuates some of the noise at a fixed frequency. An active system, on the other hand, achieves greater noise reduction while adapting to noise variations12. While a passive silencer design can be understood in the sense that it causes noise loss or noise loss. it decreases in the octave band, the design of the active system depends on the actual wavelength. For this reason, analyzes in at least 1/3 of an octave band are required to anticipate active or active / passive system requirements. In addition, it is urgent to know the exact frequency of any pure tones beyond which there are already higher order modes for a given fan channel size, since a single channel active system will not achieve complete noise cancellation above that frequency. The following parameters are monitored for correct application of the active noise cancellation system:

1) power source noise

2) the upper frequency of the noise to be reduced

3) knowledge of the audio component to be suppressed

4) measurement, respectively. noise analysis in at least 1/3 or even narrower octave range. Based on this information, it is possible to design and assume implementation of the system.

BRIEF DESCRIPTION OF THE DRAWINGS

Giant. 1 shows a schematic view of a centrifugal fan utilizing the teachings of the present invention.

Giant. 2 is a plan view of the fan of FIG. 1

Fig. 3 is a schematic diagram of an axial fan utilizing the teachings of the invention.

Figure 4 is a side view of the fan of Figure 3

Giant. 5 is a side view of one embodiment of the invention in a centrifugal fan.

Fig. 6 is another side view of a centrifugal fan to which the present invention is applied.

Giant. 7 shows a double transverse arrangement of a loudspeaker assembly.

Giant. 8 illustrates another dual arrangement of loudspeaker assembly.

Giant. 9 shows a radial fan utilizing the present invention.

Giant. 10 shows a double loudspeaker arrangement according to the present invention in a radial fan.

Fig. 11 is a radial fan utilizing the teachings of the present invention.

Giant. 12 shows another two-speaker arrangement according to the present invention.

Giant. 13 shows the dimensions of a centrifugal fan and finally

Giant. 14 is a graph of selection criteria.

DETAILED DESCRIPTION OF THE INVENTION

Figures 1 and 2

Figure 1 shows an example of the invention applied to a centrifugal fan 10. The clearance between the fan impeller and the surrounding housing 12 is far less than that of conventional fans in order to improve the efficiency of the fan 10. The small clearance results in a pressure difference at the fan 13 and This generates tonal noise. A noise source, generally referred to as a transducer 14, is preferably located as close as possible to the vent 13, either directly at the vent 13 or through a suitable channel in the form of a pipe, sleeve or ring. The noise canceling sound source may consist of one or more loudspeakers, indicated by positions 15 and 16 in FIG. 1, or piezoelectric elements. The short-length tapered channel 17 provides acoustic coupling at high frequencies.

As noted, the efficiency of the fan 10 has been improved by reducing clearance in the fan itself, such as between the impeller and the fan housing 20, between the impeller blades and armrests 51 as shown in Fig. 3 and between the impeller blades and the shutter 13 of Fig. 1. The smaller these wills, the louder the tonal noise. Noise is eliminated at both the fan inlet 22 and the outlet 23.

A sound sensor, such as a microphone or piezoelectric element 24, is built into the fan to provide a deviation signal that measures the efficiency of the active noise removal system. The exact position of the sensor may vary as long as it is outside the turbulent flow area and measures a composite sound level composed of fan noise and sound from the noise removal system. An active fully adaptable noise cancellation control unit 25 provides a jamming signal to a transducer 14, forming a jamming source, which reduces the level of the offset signal. The active control unit may be of the synchronous type as described in U.S. Pat.

878 188 or as a single non-synchronous type sensor, described by Ziegler in U.S. patent application Ser. No. 477 432.

Giant. 3 and 4 show the invention applied to the axial fan 50. Again, the clearance 51 between the blade edges 52 and the surrounding housing 53 is reduced to increase the efficiency of the fan. Here again, the resulting tonal noise is generated as a result of the pressure differentials as the blades pass around the fan supports 54.

A short length cone channel 55 is used for acoustic coupling to remove noise at the desired frequencies. These noises are often noises at frequency and their harmonics, due to the passing of the blades around the supports 54, although noises may also occur due to the rotational speed of the fan shaft. A noise source such as speakers 56.57 is located directly in the fan housing or in a duct connected to the fan. The noise cancellation source may consist of loudspeakers operating in the field of sound audibility or piezoelectric elements. An audio sensor 58 or 59, such as a microphone providing a bias signal and an active control unit, are used as described in connection with a centrifugal fan.

Further variants of the application of the invention in centrifugal fans are shown in Figures 5 to 8.

FIG. 5 shows a fan housing 60 with an active noise control unit 61 coupled to a loudspeaker 62 and a cone channel 63 extending at a fan housing tongue 64. The microphone 65 is located outside the cabinet - above it. The speed sensor 66 measures the speed of the blade fan.

In Fig. 6, the fan housing 67, with vanes 68, has a pair of loudspeakers 69 and 70 that are located on opposite sides of the exhaust chamber 71 so as to eliminate the noise generated due to the tight play 72 between the vanes and the housing. The active noise control unit 73 is coupled to the loudspeakers 69 and 70 as well as the speed sensor and microphones 74 and 75. The signals from both microphones are measured and analyzed by the active noise control unit 73 for maximum elimination of all tonal noises.

Giant. 7 shows a fan housing 76 and a vane fan 77 in a substantially similar configuration to that shown in FIG. 6, with two loudspeakers 78,79 seated on the exhaust line 80, an active noise control unit 81, a speed sensor 82, and a microphone 83 The main difference with this arrangement is that the speakers are arranged transversely.

Giant. 8 shows a fan housing 84, a vane fan 85, and two microphones 86.87 connected to a control unit 88 having inputs from sensors 89 and outputs to loudspeakers 90.91 opposite each other on channels 92.93 that deliver audio to the tongue 94 a fan to disturb the noise generated as a result of the small clearance 95.

Figures 9 to 12 show various variants of loudspeaker mounting and microphone placement for axial fans. Figure 9 shows an axial fan 100 having vanes 101 and a housing 102 with support members 103. A speed sensor 104 and a downstream microphone 105 are coupled to a control unit 106, e.g., manufactured by Noise Cancellation Technologies, Inc. and designed by NCT 2000. The control unit 106 is coupled to a loudspeaker located next to the fan housing 102 to interrupt all tonal noises.

Giant. 10 shows a fan 110 provided with blades 111 and housing 112, disposed in the channel 113. The speed sensor 114 and two ⁿ Y mikrofo16 115 and 116, one positioned in the direction of air flow, the second upstream, i.e. before and behind the impeller, are connected to an active noise cancellation control unit 116 that controls the speakers 117 and 118.

In Fig. 11 there is an axial fan 120 having a cylindrical housing 121 and vanes 122 around the motor drive 123. The control unit 124 receives speed information through the sensor 125 and the tonal noise from the microphone 126. The loudspeaker 127 immediately abuts the impeller in the air flow direction motor drive 123.

Figure 12 shows an axial fan 130 with a cylindrical housing 131 and blades 132. It is equipped with a motor drive 133 and speakers 134 and 135 located at the front and rear thereof. The speakers are controlled by an active control unit which responds to the fan speed via sensor 137 and measures by microphones. 138 and 139 fan noise. One of the microphones 138 is located in the air stream upstream of the fan, the other 139 downstream of the fan.

Selected embodiments of the invention have been described in detail above.

It will be appreciated, however, that based on the teachings of the invention, other variants and alternatives could be developed using conventional experience in the art. It is therefore to be understood that the present arrangements are intended to be illustrative only, and not limiting, of the scope of the invention as set forth in the appended claims.

Claims (7)

PATENT Claims S ~ i An apparatus for actively removing noise generated by the rotation of vanes in a fluid moving system, increasing system efficiency, the apparatus comprising: - means for maintaining fluid within a confined and defined space, means for accelerating and compressing air in said space so as to reduce broadband noise while transmitting the tonal component as the predominant source of noise - means for monitoring the passage frequency of the blades - means for detecting the noise generated by the means for accelerating and compressing.for pushing the fluid through the confined and demarcated space and for generating a signal carrying information about the noise - loud reproductive means adjacent to the fluid surrounding means - electronic control means for receiving a signal carrying information on the blade passage frequency and for receiving a signal corresponding to the generated noise, and also for producing an equivalent anti-noise delivered to said loud reproduction means, whereby the generated increased noise is acoustically reduced by this equivalent anti-noise sound while increasing the efficiency of the fluid actuation system 2/13 0BR.2 OJ 2. The apparatus of item 1, wherein the means for accelerating and compressing the fluid is a centrifugal fan having little clearance between the housing and the rotating part provided with the vanes. 3/13 OJ • w σ »» ο JAiO INIS VTA OHBAOlSXWQyd avy □ 3. The apparatus of item 2, wherein the noise detecting means comprises at least one microphone means ^ 3 'I.e - > WHAT Q —H 7½ 72. WHAT > O CC □ m -WITH O o. cc ') o c_. czx [<. · * C r— 1 O cz 1 4. The apparatus of item 3, wherein the microphone means comprises two microphones, one of which is located near the inlet of the fan housing, while the other is located near the outlet of the moving fluid from said system. 5/13 5. II '9 t O1SOQ FROM 8 Π 0. • f’o 5. The apparatus of item 2, wherein the loudspeaker means comprises at least one loudspeaker disposed in a helical fan housing transition to an exhaust duct adapted to produce a sound counteracting the frequency, phase and amplitude of the tonal noise component. 6/13 W '• w —--—) JAIOINÍSVÍA ·, avy or to r7 5. II '9 L 03 ^ 00 y 9 o R 0 0 i r- -tyčj 6 .11 '9 L 01§0Q y 9Γ, fi n <o LO (oo ' I (ok DONE 6. The apparatus of item 1, wherein the fluid drive system is an axial fan built into the flow channel body. 7. The apparatus of item 6, wherein the noise detecting means comprises at least one microphone means. 8. The apparatus of item 7, wherein the microphone means comprises two microphones, one located upstream of the blower and the other downstream of the fan impeller. 9. The apparatus of item 6, wherein the loudspeaker means comprises at least one loudspeaker incorporated in the center of the axial fan. 10. The apparatus of item 6, wherein the loudspeaker means comprises two loudspeakers built in the direction and direction of the loudspeaker. upstream of the blowing fluid. 11. A fully adaptable active noise abatement system for rotating blades in a gas moving device while increasing the efficiency of the device, the system comprising: a housing forming means limiting the fan 6 to reduce broadband noise while the tonal noise component is transmitted - means for transporting gas in said space in such a way as to reduce any broadband noise, the latter being released - a tracking means adapted to monitor the frequency of the gas conveying means and to generate a signal carrying information about that frequency - noise-activated means for detecting the noise generated by the movement of the gas through the housing-forming means and for generating a signal carrying information about the noise - a loudspeaker means located near the means forming the housing, and - an adaptive control means for receiving, on the one hand, signals carrying the frequency information of the gas conveying means, on the other hand, signals from the noise activated means, wherein the adaptive control means continuously generates an audio signal of opposite and equal amplitude to tonal noise; increases the efficiency of the gas conveying device. 12. The system of item 11, wherein said device is a centrifugal fan and the gas is air. 13. The system of items 11, wherein said device is a centrifugal fan, wherein the loudspeaker means is located near the transition of the helical-shaped housing into the exhaust duct and is adapted to produce a sound that counteracts the frequency, phase and amplitude of tonal noise. 14. The system of item 11, wherein the loudspeaker means is located outside the means forming the fan housing so that it is out of the moving gas stream. 15. The system of item 14, and wherein the means forming the housing comprises a short channel. 16. The system of clause 15, comprising both a noise-activated means comprising two microphones adjacent to the housing-forming means, each microphone adapted to generate a signal representing the noise caused by the gas conveying device and an adaptable control means for combining the two. signals, in order to increase the ability to continuously and as needed produce a signal for the loudspeaker means, which then generates a sound of opposite and equal amplitude. 17. The system of item 16, wherein said device is a centrifugal fan. 18. The system of item 11, wherein said device is an axial fan built into the flow channel, wherein the noise detecting means comprises at least one microphone means. 19. The system of clause 18 having two microphone means disposed adjacent the housing forming means. 20. The system of item 18, wherein the loudspeaker means comprises at least one loudspeaker attached to the hub center of said axial fan. 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