JPH0361137A - Interphone conversation device in car room - Google Patents

Abstract

PURPOSE:To securely suppress noise in an unnecessary frequency band and obtain a comfortable conversation state by providing a high pass filter to damp the unnecessary frequency band for usual conversation in a circuit system that transmits the voice signal converged to a microphone to a speaker. CONSTITUTION:A conversation means is constructed from a microphone 1, a microphone amplifier 2 that amplifies the voice signal converged by the microphone, a high pass filter 3 that only passes frequency, for example, not less than 500Hz, a low pass filter 4 that only passes frequency, for example, less than 5kHz, a buffer amplifier 5 for impedance conversion, an attenuator 6 that damps the signal level of the voice signal passes through respective filters 3, 4, a power amplifier 7, and a speaker 8. Then using two sets of this conversation means, respectively installing the microphones 1 in the vicinity of a driver's seat and a rear seat, and the speakers 8 in the vicinity of the rear seat and in the vicinity of the driver's seat, a conversation device is constructed to make the conversation between a driver and a rear seat occupant possible.

Description

[Detailed Description of the Invention] [Summary] Regarding the in-vehicle intercom communication device, vibration noise due to engine rotation and vehicle vibration, abnormal noise due to direct vibration of the microphone when starting the engine, etc., as well as ignition pulse and alternator noise, etc. In order to reliably suppress the sound pressure in unnecessary audio bands, the circuit system that sends the audio signal picked up by the microphone to the speaker is
It is equipped with a high-pass filter to attenuate frequency bands unnecessary for normal conversation.

(1) [Industrial Application Field] The present invention relates to an in-vehicle intercom communication device, and more particularly to an in-vehicle intercom communication device that eliminates noise and improves the S/N ratio.

[Conventional technology]

Conventionally, this type of in-vehicle interphone communication device has been known to pick up body vibrations, engine noise, etc. depending on the way and position of the microphone when the interphone is used while the vehicle is running (including idling), causing noise on the interphone. Appears as. These noises are caused by vibrations due to engine rotation and power abnormalities caused by the ignition part, alternator, etc.

[Problem to be solved by the invention]

The present invention was made to solve such problems,
In the above-mentioned interphone communication device, a comfortable communication state can be achieved by establishing a state in which normal conversation does not feel strange, and by suppressing (2) (attenuating) unnecessary signals (noise) outside the necessary voice band. This is how it was done.

[Means to solve the problem]

In order to solve this problem, according to the present invention, a high-pass filter is provided in the circuit system that sends the audio signal picked up by the microphone to the speaker to attenuate frequency bands unnecessary for normal conversation. , an in-vehicle intercom communication device is provided.

[For production]

According to the above configuration, the high-pass filter can reliably prevent interference with the interphone communication device due to intrusion of vehicle engine noise, vibration noise, etc. during normal operation.

〔Example〕

FIG. 1 is a block diagram illustrating the overall configuration of the device of the present invention, in which 1 is a microphone, 2 is a microphone amplifier for amplifying the audio signal picked up by the microphone (3), and 3 is a microphone amplifier for amplifying the audio signal picked up by the microphone (3), for example, 500 Hz or higher. 4 is a low-pass filter that passes only frequencies below 5 kHz, 5 is a buffer amplifier for impedance conversion, and 6 is the audio that has passed through the high-pass filter 3 and the low-pass filter 4. 7 is an attenuator that attenuates the signal level of the signal; 7 is a power amplifier; and 8 is a speaker. Then, another set of the same configuration is installed in the vehicle, one set has microphone 1 near the driver's seat and speaker 8 near the rear seat, and the other set has microphone 1 near the rear seat and speaker 8 near the driver's seat. It is installed near the seat.

As shown in FIG. 1, when microphone 1 picks up a signal containing a mixture of voice and noise, these signals are transmitted to microphone amplifier 2, high-pass filter 3, low-pass filter 4, buffer amplifier 5, and attenuator 6. After the power is amplified by the power amplifier 7, the speaker 8 is driven to output sound.

In this case, the high-pass filter 3 (an example of its frequency (4) level characteristics is shown in FIG. (corresponding to the area in part A in the figure).

In addition, unnecessary audio bands such as ignition pulses and alternator noise (corresponding to the area C in Figure 2) are attenuated by the low-pass filter 4 (an example of its frequency-level characteristics is shown in Figure 3 (C)). let

The frequency band of the vibration sound caused by the engine rotation is idling B (engine rotation speed of 600 rpm to 800 rpm).
rpm) 10Hz-13Hz, constant speed state (engine speed 1500rpm to 250orpm) 25Hz
~42flz (250Hz up to the 10th harmonic)
420Hz>, high rotation state (engine rotation speed 10.
00Orpm>, the frequency is about 170Hz, and these vibration sounds are removed by the high-pass filter 3.

In this way, by combining the high-pass filter 3 and the low-pass filter 4, it is possible to attenuate the abnormal noise generated from the vehicle as described above, and realize a good communication situation (5). That is, the noise bands corresponding to parts A and 0 in FIG. 2 are cut by the low-pass filter 4 and high-pass filter 3, and only the signals in the voice band necessary for conversation (corresponding to part B in FIG. 2) are cut. The signal is supplied to the speaker 8.

〔Effect of the invention〕

According to the present invention, even if a microphone picks up abnormal noise such as car engine noise or vehicle vibration noise, by rapidly attenuating frequency bands unnecessary for conversation, the noise in the unnecessary frequency bands can be reliably suppressed. It can be suppressed.

[Brief explanation of drawings]

1 is a block diagram illustrating the overall configuration of the present invention, FIG. 2 is a diagram illustrating the frequency-level characteristics of the device shown in FIG. 1, and FIG. 3 is a diagram illustrating the high-pass filter and low FIG. 3 is a diagram showing frequency level characteristics of a pass filter. (6) (Explanation of symbols) 1... Microphone, 3... High pass filter, 5... Buffer amplifier, 7... Power amplifier, 2... Microphone amplifier, 4... Low Pass filter, 6...attenuator, 8...speaker.

Claims (1)

[Claims] 1. An in-vehicle intercom communication device characterized in that a circuit system for sending an audio signal picked up by a microphone to a speaker is equipped with a high-pass filter for attenuating frequency bands unnecessary for normal conversation.