JPH03123109A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To prevent failing to listen to a sound due to irregular and short time external noise by varying an amplification factor of a variable amplifier of an output stage with use of a differential component of an envelope detecting output of a reproducing sound signal and an envelope detecting output of the external noise. CONSTITUTION:A reproduced sound signal amplified by an amplifier 7 is delayed by a delay circuit 10 for a prescribed time and outputted to an envelope detecting circuit 11. A built-in microphone 13 collects external noise generated from an irregular/short time noise source 17 and the sound generated from the loudspeaker 9a of a monitor 9, and outputs them to an envelope detecting circuit 15 through a microphone amplifier 14. A differential amplifier 12 takes a deviation of outputs of the envelope detecting circuits 11, 15 and amplifies them, and in the case the output of the differential amplifier exceeds a certain threshold, an amplification factor of a variable amplifier 16 becomes larger, and the level of an outputted sound signal becomes larger. In such a way, for instance, in the case there is an irregular and short time noise such as produced by the train passing through, a sound becomes larger automatically, and it can be listened without fail.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention provides a built-in microphone (hereinafter referred to as a microphone).
The system separates only the noise from the input signal, amplifies the signal according to its level, and outputs it. When there is irregular, short-term noise, such as when a Shinkansen passes, it automatically increases the volume and makes it possible to avoid missed sounds. The present invention relates to a magnetic recording/reproducing device in which the magnetic recording device is free from magnetic recording.

[Conventional technology]

FIG. 3 is a block diagram of the audio reproduction system of a conventional magnetic recording and reproducing device.The reproduced audio signal reproduced from the audio head 1 is amplified by the hesodio amplifier 2, and then passes through the bandpass filter 3 and the FM limiter 4. , demodulated by the demodulation circuit 5.

The demodulated audio signal has its noise reduced by a noise reduction circuit 6, is amplified by an amplifier 7, and is then outputted from an audio output terminal 8 to a monitor 9.

[Problem to be solved by the invention]

Since the audio playback system of the conventional magnetic recording and playback device is configured as described above, the output of the audio playback system is output from the audio output terminal 8.
For example, if there is irregular, short-term (about a few seconds) external noise, such as the noise when a bullet train passes, the sound during that period cannot be heard and the monitor 9 The problem was that as you turned up the volume, the noise would disappear, and you would either end up hearing it or have to rewind the tape and play it again.

This invention was made to solve the above problems, and when there is irregular, short-term external noise, the audio output is automatically increased to prevent the audio from becoming distorted. The object of the present invention is to obtain a magnetic recording/reproducing device that can perform the following steps.

[Means to solve the problem]

The magnetic recording and reproducing device according to the present invention includes a first envelope detection circuit that performs envelope detection after delaying a reproduced audio amplification output signal, and a second envelope detection circuit that performs envelope detection of irregular and short-term external noise input to a built-in microphone. an envelope detection circuit, a differential amplifier that amplifies the outputs of the first and second envelope detection circuits by taking the deviation, and a variable amplifier that is provided in the audio output stage and whose amplification factor changes depending on the output of the differential amplifier. It is something that

[For production]

The magnetic recording/reproducing device according to the present invention uses a differential amplifier to take and amplify the deviation between the first envelope detection output of the reproduced audio signal and the second envelope 46-wave output of external noise detected by the built-in microphone. By changing the amplification factor of the variable amplifier in the output stage using the differential component, if there is irregular or short-term external noise, increasing the amplification factor will raise the level of the reproduced audio signal, making it difficult to hear the reproduced audio due to the noise. It works to prevent it from disappearing.

〔Example〕

Embodiments of the magnetic recording/reproducing apparatus of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of one embodiment. In FIG. 1, the same parts as those in FIG. 3 are given the same reference numerals to avoid redundant explanation of the structure, and mainly the parts different from those in FIG. 3 will be described.

As is clear from comparing Figure 1 with Figure 3,
In the figure, parts numbered 1 to 9 are the same as in Figure 3,
The parts indicated by reference numerals 10 and after are newly added to the structure of FIG. 3, and are the parts that characterize this embodiment.

That is, 10 is a delay circuit that delays the reproduced audio signal amplified by the amplifier 7 for a predetermined time and outputs it to the envelope detection circuit 11. It is designed to be added to the negative input terminal.

In addition, a new microphone is provided as a built-in microphone 13, and this built-in microphone 13 collects the external noise generated from the irregular/short-time noise source 17 and the sound generated from the speaker 9a of the monitor 9. It is designed to output to .

The output of this microphone amplifier 14 is the envelope detection circuit 1
It is designed to output to 5. The output of the envelope detection circuit 15 is input to the positive input terminal of the differential amplifier 12.

When the outputs of both envelope detection circuits 11 and 15 are input to a differential amplifier 12, a deviation is taken there, amplified, and then output to a variable amplifier 16.

This variable amplifier 16 is inserted between the output terminal of the amplifier 7 and the audio output terminal 8. That is, the variable amplifier 7 is provided at the output stage of the magnetic recording/reproducing device, and the differential amplifier 12
The amplification factor changes depending on the output of the amplifier 7, and the level of the audio signal output from the amplifier 7 is varied.

Next, the operation will be explained. After the reproduced audio signal reproduced from the audio head 1 is amplified by the hesode amplifier 2,
The signal passes through a bandpass filter 3 and an FM limiter 4, and is demodulated by a demodulation circuit 5.

The audio signal demodulated by this demodulation circuit 5 passes through a noise reduction circuit 6 and is amplified by an amplifier 7.

The output of this amplifier 7 is input to a variable amplifier 16 and a delay circuit 10. In the delay circuit 10, the audio signal is output from the audio output terminal 8 to the monitor 9, and the audio output from the speaker of the monitor 9 is input from the built-in microphone 13.
The delay until the signal is input to the microphone amplifier 14 is delayed.

The audio signal delayed by the delay circuit 10 is subjected to envelope detection by the enrove detection circuit 11 and then input to the negative input terminal of the differential amplifier 12.

On the other hand, the built-in microphone 13 receives the audio output from the speaker 9a of the monitor 9 and the noise from the irregular/short-time noise source 17, amplifies it with the microphone amplifier 14, and then performs envelope detection with the envelope detection circuit 15. This envelope-detected microphone input signal is input to the positive input terminal of the differential amplifier 12.

FIG. 2 shows the signal waveforms of each part. Figure 2 (al is the output waveform of the delay circuit 10, Figure 2 (bl is the output waveform of the microphone amplifier 14, Figure 2 (C1 is the reproduced audio signal envelope detection waveform, Figure 2 Tdl is the microphone input signal envelope detection waveform) 2(C) and 2(d+) are input to the negative input terminal and positive input terminal of the differential amplifier 12, respectively. tel in FIG. 2 is the output waveform of the differential amplifier 12. .

The output of this differential amplifier 12 is input to a variable amplifier 16. When there is no input signal, the amplification factor of the variable amplifier 16 is 1, and the input audio signal is outputted to the audio signal output terminal 8 as is.

On the other hand, if noise is input and the output of the differential amplifier 12 is above a certain threshold (see tel in Figure 2), the amplification factor of the variable amplifier 16 increases, the level of the output audio signal increases, and the output of the differential amplifier 12 increases. The result is as shown in Figure 2 ffl. This prevents the audio signal from becoming loud and inaudible when there is noise.

〔Effect of the invention〕

As described above, according to the present invention, a signal obtained by delaying the reproduced audio signal and envelope-detecting it in the first envelope detection circuit, and a signal obtained by enveloping the external noise collected by the built-in microphone in the second envelope detection circuit. Based on the deviation from When there is time noise, the sound automatically becomes louder and has the effect of preventing the sound from becoming inaudible.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a magnetic recording and reproducing apparatus according to an embodiment of the present invention, and FIG. 2 is a signal waveform diagram of each part of the same embodiment.
FIG. 3 is a block diagram of a conventional magnetic recording/reproducing device. 1...Audio head, 4...FM IJ mitter, 5
...Demodulation circuit, 7...Amplifier, 9...Monitor, 1
0...Delay circuit, 11.15...Envelope detection circuit, 12...Differential amplifier, 16...Variable amplifier,
17...Irregular/short-time noise source. In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] a demodulation circuit that demodulates the audio signal reproduced by the audio head, an amplifier that amplifies the audio signal demodulated by the demodulation circuit, and a delay circuit that delays the output of the amplifier for a predetermined time;
a first envelope detection circuit that performs envelope detection on the output of this delay circuit; a built-in microphone that collects external noise; a second envelope detection circuit that performs envelope detection on the output of this built-in microphone; a differential amplifier that takes the deviation of the output of the envelope detection circuit and amplifies it; and a differential amplifier that is provided between the output terminal of the amplifier and the monitor and amplifies the output of the amplifier by varying the amplification factor according to the output of the differential amplifier. A magnetic recording/reproducing device equipped with a variable amplifier.