JPH0370406B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a public address system used in places where ambient noise is high and the noise level fluctuates, such as in tunnels, station platforms, and waiting rooms.

1. Configuration of a conventional example and its problems FIG. 1 shows a block diagram of a conventional public address system. In FIG. 1, 1 is a microphone, 2 is a microphone amplifier, 4 is a speaker group in which individual speakers 4a to 4d are connected in parallel, and microphone 1, microphone amplifier 2, main amplifier 3, and speaker group 4 are connected in series. There is.

The operation of the public address system configured as described above will be explained below.

First, amplified sound entering the microphone 1 is amplified by the microphone amplifier 2 and the main amplifier 3, and reproduced by each of the speakers 4a to 4d of the speaker group 4. At this time, the level of the reproduced sound was changed by changing the volume of the main amplifier 3 according to the noise level in the amplification area.

However, when trying to amplify the sound over a wide area, the noise level changes depending on the time of day, so in order to maintain clarity, it is necessary to constantly monitor the noise level and control the level of the reproduced sound. Because the noise level varies depending on the location where the sound is being amplified, in order to improve the clarity of the amplified content throughout, it was necessary to play back at a very high level so that the loud noise level could be constantly masked. Therefore, the reproduced sound becomes too loud during times when the noise level is low or in amplified areas, so the reality is that the level of the reproduced sound is adjusted according to times when the noise level is low. This has the disadvantage that the reproduced sound is masked by noise and its clarity is reduced.

Purpose of the Invention The present invention has been made in view of the above-mentioned drawbacks, and even during amplification, the noise level near the speaker to be reproduced is detected and the level of the reproduced sound is controlled according to the noise level, so that the sound quality is achieved regardless of the noise level. It is an object of the present invention to provide a public address system capable of obtaining amplified sound having high intelligibility.

Structure of the Invention In order to achieve the above object, the loudspeaker of the present invention uses a noise detection sensor that detects noise by detecting the movement of the diaphragm of the loudspeaker as a voice coil in order to detect noise around the loudspeaker. Alternatively, a high frequency device and a low frequency device are provided independently to separate the noise detection sensor into a loudspeaker signal and a noise signal, and the reproduction level of the loudspeaker is constantly adjusted according to the magnitude of the noise signal level. With this configuration, amplified sound with high clarity can be obtained regardless of fluctuations in the noise level around the loudspeaker.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 is a block diagram of a loudspeaker system according to a first embodiment of the present invention. In FIG. 2, 1 is a microphone that outputs a loudspeaker signal, 22 is a microphone amplifier that amplifies the loudspeaker signal, and 5a to 5d are automatic gain control circuits connected to the microphone amplifier 2 and that control the gain of the amplified loudspeaker signal. 6a~
6d is the main amplifier, 7a to 7d are high frequency devices,
8a to 8d are speakers installed in amplification locations, respectively, and include automatic gain control circuits 5aa to 5d, main amplifiers 6a to 6d, high frequency amplifiers 7a to 7d, and
Loudspeakers 8a to 8d are connected in series. 9a to 9d are low frequency devices, 10a to 10d are amplifiers, 11a to 11d are rectifier circuits, speakers 8a to 8d, low frequency devices 9a to 9d, and amplifier 10.
a to 10d and rectifier circuits 11a to 11d are connected in series, respectively, and the rectifier circuits 11a to 11d feed back their output signals (or levels) to automatic gain control circuits 5a to 5d.

FIG. 3 is a block diagram of the main parts of this embodiment, showing the connection state between each speaker 8a to 8d, high frequency amplifiers 7a to 7d, and low frequency amplifiers 99a to 9d.

In FIG. 3, 7 is a high frequency device, 8 is a speaker, and 9 is a low frequency device. They are the same parts. 12 is a voice coil, 13 is a diaphragm, 14 is a magnet,
The voice coil 12 is electrically connected to the high frequency devices 7a to 7d and the low frequency devices 9a to 9d.

The operation of this embodiment configured as above will be described below.

2 and 3, first, a loudspeaker signal outputted from the microphone 1 is amplified by the microphone amplifier 2 and is then amplified by the automatic gain control circuits 5a to 5.
d, is amplified by main amplifiers 6a to 6d, and reproduced by speakers 8a to 8d with low frequency components cut off by high frequency amplifiers 7a to 7d. The diaphragm 13 of the speaker 8 vibrates not only due to the loudspeaker signal but also due to ambient noise, and an electromotive force is generated in the voice coil 12. Since this electromotive force includes a loudspeaker signal component with low frequency components cut off and an ambient noise signal component, the low-frequency wave generator 9 is used to extract this noise signal component. The noise signal amplifiers 10a to 10d amplify the signal, and the rectifier circuits 11a to 11d convert the signal into a DC voltage, which is input to the automatic gain control circuits 5a to 5d. The automatic gain control circuits 5a to 5d automatically adjust the reproduction level of the loudspeaker signal in accordance with the level of the noise signal converted into a DC voltage. Here, the high frequency device 7a
The cut-off frequency of the filters 7d to 7d is 600 Hz, and the cut-off frequency of the low frequency converters 9a to 9d is approximately 200 Hz.

As described above, according to this embodiment, the electromotive force generated in the voice coil 12 due to the vibration of the diaphragm 13 of the speaker 8 is detected, and the loudspeaker signal and noise signal included in this electromotive force are transmitted to the high-frequency amplifier 7. and low frequency generator 9
Since the automatic gain control circuits 5a to 5d can automatically change the playback level of the amplification signal according to the level of the noise signal, even if the surrounding noise level changes depending on the time of day, A reproduction level with good clarity that is not masked by ambient noise can be obtained at all times. Also, voice coil 1
Since the noise level is detected from the electromotive force generated in the loudspeaker 8, there is no need to provide any other detection means for detecting the noise level, and the voice coil 12 of the loudspeaker 8 also serves as a noise detection sensor. Therefore, manufacturing costs etc. can be reduced.

FIG. 4 is a block diagram of main parts of a loudspeaker according to a second embodiment of the present invention, showing the structure of a voice coil of a speaker.

In FIG. 4, 15 is a voice coil for applying amplified signal, and 16 is a whistle coil for noise signal detection.The voice coil 15 for applying amplified signal reproduces the amplified signal, and the voice coil 16 for detecting noise signal detects the noise signal. .

FIG. 5 is a schematic sectional view of a speaker of a public address system according to a third embodiment of the present invention.

In FIG. 5, the same members as those in FIG. 3 are given the same numbers and their explanations will be omitted. Reference numeral 17 denotes a vibration detection sensor provided in a non-vibration portion of the speaker 8. In this embodiment, the noise is detected using the output from the vibration detection sensor 17, instead of using the electromotive force generated by the vibration of the voice coils 12 and 16 as in the first and second embodiments.

Here, as the vibration detection sensor 17, an eddy current detector, a capacitance detector, an optical sensor, etc. can be used, and many other sensors can be used.

In all of the above embodiments, any number of speakers 8 may be used, and in this case, the reproduction level is adjusted for each speaker. In addition, each speaker 8a~
It is also possible to provide a delay circuit corresponding to the propagation time corresponding to the arrangement interval of 8d.

Furthermore, in each of the above embodiments, each main amplifier 6a
- 6d are provided with respective high-frequency amplifiers 7a-7d at their output stage, but the connection order is reversed, and each main amplifier 6a-6 is provided at the output stage of each high-frequency amplifier 7a-7d.
d may be provided.

Effects of the Invention As described above, according to the loudspeaker of the present invention, the movement of the diaphragm of the loudspeaker is detected using the noise detection sensor, and the loudspeaker signal and the noise are detected using the high-frequency wave device and the low-frequency wave device. The signal is separated, and the automatic gain control circuit automatically adjusts the playback sound level according to the ambient noise signal level, regardless of the loudspeaker signal level, so it is not always masked by ambient noise. You can obtain playback sound with excellent clarity. In particular, by using the voice coil of the loudspeaker as a noise detection sensor, there is no need to provide other dedicated noise detection means, and manufacturing costs can be reduced, which has a significant effect.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a conventional loudspeaker, FIG. 2 is a block diagram of a loudspeaker according to a first embodiment of the present invention, FIG. 3 is a configuration diagram of the main parts, and FIG. FIG. 5 is a schematic sectional view of a speaker of a loudspeaker according to a third embodiment of the present invention. 5a-5d... automatic gain control circuit, 7, 7a-
7d... High frequency device, 8, 8a to 8d... Speaker, 9, 9a to 9d... Low frequency device, 11a to 1
1d... Rectifier circuit, 12... Voice coil, 15
...Voice coil for applying amplified signal, 16...Voice coil for detecting noise signal, 17...Sensor for detecting vibration motion.

Claims (1)

[Claims] 1. To detect noise around the loudspeaker,
A noise detection sensor that detects noise by detecting the movement of the diaphragm of the loudspeaker is provided together with the voice coil or independently, and a high frequency device that blocks low frequency components of the loudspeaker signal and detects ambient noise signals. and an automatic gain control circuit that controls the amplification sound level according to the magnitude of the level of the detected noise signal; A loudspeaker system, characterized in that the loudspeaker separates a loudspeaker signal into a loudspeaker signal and a noise signal, and always adjusts the reproduction level of the loudspeaker according to the magnitude of the noise signal level.