JPS58222697A - Pickup microphone circuit of bone conduction audio signal - Google Patents

Abstract

PURPOSE:To improve the noise performance and the sound quality and to prevent howling, by using a notch filter attenuating the sensitivity of the resonance frequency of the frequency characterstics and frequencies in the vicinity thereof. CONSTITUTION:An audio signal of the user outputted from an ear microphone (EM)1 is transmitted to other radio device via a radio device 3, outputted as a voice from a speaker 4 or inputted to a voice input device 5. A filter 2 comprises a high pass filter 2a forming a frequency characteristic A, a low pass filter 2b forming a frequency characteristic B and the notch filter 2c forming the notch characteristic of the resonance frequency of about 4kHz of the frequency characteristic of the EM1 and frequencies in its vicinity. The audio signal extracted from the EM1 has a frequency characteristic C through the filter 2, and the frequency characteristic where the uniform sensitivity is given to the resonance frequency of about 4kHz and the frequency in its vicinity, is attained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a bone conduction audio signal pickup microphone circuit for the purpose of improving noise resistance, improving sound quality, and preventing howling.

Bone conduction audio signal sound pickup microphones have several resonant frequencies within the audio frequency band used, and the sensitivity reaches its maximum at the resonant frequencies, resulting in poor noise resistance and poor audio performance.
It still causes howling.

Conventionally, a low-pass filter with a cutoff frequency lower than the resonant frequency is used, but since the sensitivity of the resonant frequency of the bone conduction audio signal pickup microphone is extremely high, it is necessary to reduce the sensitivity so that it does not affect the usage. could not be lowered sufficiently. Also, cut 171
Because the frequency was set in the low range, the high frequency response was not very good.

The present invention uses a notch filter that attenuates the sensitivity of the resonance frequency of the frequency characteristic of a bone conduction audio signal pickup microphone and frequencies around the resonance frequency to obtain a frequency characteristic of approximately uniform sensitivity.

Improves noise resistance, improves sound quality, and prevents howling.

Bone conduction audio signal pickup microphones are of acceleration type, velocity type, etc., and due to the structure of the signal sound sensor, there are several resonance points within the audio frequency band used.

It is most effective to use a notch filter that has a notch effect at the same frequency as the resonant frequency of the signal sound sensor, but in practice it is difficult to manufacture the same filter, so it is difficult to manufacture a notch filter with completely uniform sensitivity. It cannot be a frequency characteristic. Therefore, even if uniform sensitivity cannot be obtained within a range that does not impede use, it is sufficient to obtain noise resistance, improved sound quality, and anti-howling effect.

The embodiments of the present invention will be explained in the accompanying drawings.

Filter 2 is connected to the acceleration type bone conduction audio signal sound pickup type ear microphone l, and the radio device 3 is connected to the filter 2.
．． A loudspeaker 4 or an audio input device 5 is connected. The user's voice signal output from the ear microphone is transmitted through the radio 3 to another radio (not shown), and then transmitted to the loudspeaker 4.
It is output as a voice or input into the voice input device 5.

As shown in FIG. 3, the filter 2 includes a bypass filter 2a that forms a frequency characteristic A, a low-pass filter 2b that forms a frequency characteristic B, and a frequency characteristic of approximately 4 Hz of the hear microphone l (FIG. 2). Notch filter 2c that forms notch characteristics at the resonance frequency and frequencies around it
It becomes more. When the audio signal output from the ear microphone 1 passes through the filter 2, it has a frequency characteristic as shown in FIG. 4, and a frequency characteristic of uniform sensitivity is obtained at the resonance frequency of about 4 KHz and frequencies around it.

The present invention substantially eliminates the influence of the gain of the resonance frequency of the signal sound sensor of the bone conduction sound signal sound pickup microphone, so it is effective in improving noise resistance, improving sound quality, and preventing howling, and making it possible to obtain high-quality sound signals. can.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram of an embodiment of the present invention, Figure 2 is a frequency characteristic diagram of a signal sound sensor, Figure 3 is a frequency characteristic diagram of a filter, and Figure 4 is a frequency characteristic diagram of an audio signal that has passed through a filter. be. l... Bone conduction audio signal sound pickup microphone,
2... Filter.

Claims (1)

[Claims] A bone conduction voice signal sound pickup in which a notch filter is connected to a bone conduction voice signal sound pickup microphone to attenuate sensitivity at the resonance frequency and frequencies around the resonance frequency in substantially correspondence to the resonance frequency and frequencies around the resonance frequency of the microphone. Microphone circuit.