JPH02137153A - Tape recorder - Google Patents

Abstract

PURPOSE:To eliminate a malfunction by comparing the time rate of a digital sound signal exceeding a reference value with a reference rate, executing sound detection, executing the D/A conversion of the digital sound signal and recording the signal to a magnetic tape. CONSTITUTION:A sound detecting means 5 compares the digital sound signal, for which the A/D conversion of a sound signal is executed, with a reference value 52 determined in advance, for a fixed time. Then, by comparing the time rate of the digital sound signal exceeding the reference value 52 with a reference rate 55 determined in advance, the sound detection is executed. Next, this digital sound signal is temporarily accumulated in a memory means and the D/A conversion of the digital sound signal read from the memory means is executed by a tape traveling mechanism 12. Then, the signal is recorded to a magnetic tape 9. Accordingly, even when a spike-shaped noise is inputted while a sound is not outputted, the noise is not erroneously detected as the sound signal. Thus, the malfunction of tape traveling can be eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a tape recorder that detects audio and automatically starts recording.

2. Description of the Related Art In recent years, tape recorders that detect audio and automatically start recording have been developed. Furthermore, in order to prevent so-called cut-offs, where recording cannot be made due to the time delay between when the sound is emitted and when the magnetic tape starts running,
Tape recorders with audio delay means have also been developed.

A conventional tape recorder that detects audio and automatically starts recording will be described below.

FIG. 4 shows the configuration of a conventional tape recorder that detects audio and automatically starts recording, and FIG. 5 is an operational waveform diagram of the conventional example shown in FIG. In FIG. 4, 21 is a microphone for audio recording, 22 is a microphone amplifier with automatic gain adjustment means, 23 is an analog delay means using BBD,
24 is an audio detection amplifier, 25 is audio detection means, 26 is a rectifier, 27 is an integrator, 28 is a comparator, 29 is a reference value setting means using a variable resistor, 30 is a recording circuit, 31 is a recording head, 32 is a A magnetic tape, 33 is a control means, and 34 is a tape running mechanism.

The operation of the tape recorder configured as described above that detects audio and automatically starts recording will be described below.

First, before recording, the reference value setting means 29 is manually adjusted to an appropriate value so that the sound detection means 25 does not detect ambient noise and cause the magnetic tape 32 to run when no sound is being emitted. Next, when audio is input to the microphone 21, the audio is amplified by the microphone amplifier 22 with automatic gain adjustment according to the magnitude of the input signal, and the audio is amplified by the analog delay means 23.
At the same time, the microphone output is amplified by the voice detection amplifier 24, inputted to the voice detection means 25, rectified by the rectifier 26, smoothed by the integrator 26, and set a reference value in advance as shown in FIG. A comparator 28 compares the sound signal with a reference value determined by means 29, and if the sound signal is larger than the reference value, sound detection means 25 outputs a detection signal. This detection signal is input to the control means 33 and the tape running mechanism 34
causes the magnetic tape 32 to start running. On the other hand, the audio delayed by a certain period of time (tl) by the analog delay means 23 is recorded on the magnetic tape 32 through the recording circuit 30 and the recording head 31 without being cut off, as shown in FIG. Furthermore, when audio is no longer input, the audio detection means 25 stops the detection signal, and the control means 33 causes the tape running mechanism 34 to stop after a certain period of time (t2) has passed, and the magnetic tape 32 to stop running. .

Problems to be Solved by the Invention However, in the above-mentioned conventional configuration, (1) When so-called spike-like noise with a large amplitude and a narrow time width is input when no voice is being emitted, the voice detection means 25 activates the integrator 27 (2) Manually adjust the reference value setting means 29 to adjust the sensitivity of the sound detection means 25 before recording. (3) Since automatic gain adjustment is used in the microphone amplifier 22, there is a problem in that when spike-like noise is introduced during audio recording, the amplifier gain is lowered and the audio recording level is lowered.

The present invention solves the above-mentioned conventional problems. (1) There is no malfunction of running the magnetic tape even if spike-like noise is input when no sound is being emitted, and (2) there is no malfunction of running the magnetic tape before recording. It is an object of the present invention to provide an excellent voice-activated tape recorder that does not require manual sensitivity adjustment and (3) does not reduce the recording level even if spike-like noise occurs during voice recording.

Means for Solving the Problems In order to achieve this object, the tape recorder of the present invention that detects audio and automatically starts recording (1)
/D-converted digital audio signal with a predetermined reference value for a certain period of time, and detects audio by comparing the time ratio of the digital audio signal exceeding the reference value with the predetermined ratio; It is equipped with a memory means for temporarily storing audio signals, and a tape running mechanism for D/A converting the digital audio signal read from the memory means and recording it on a magnetic tape, and (2) prior to audio recording. The digital signal obtained by A/D converting the microphone amplifier output during the period when no sound is being emitted is compared with a certain reference value for a certain period of time, and the reference value is changed so that the time ratio of the digital signal exceeding the reference value becomes a predetermined ratio. The device is equipped with a configuration for setting the voice detection reference value of the voice detection means based on the reference value when the ratio matches a predetermined ratio, and (3) a digital signal obtained by A/D converting the output of the microphone amplifier. This device has a configuration that controls the gain of the microphone amplifier by comparing the signal with a predetermined reference value for a certain period of time and comparing the time ratio of the digital signal exceeding the reference value with the predetermined ratio.

Effects The present invention has the above-described configuration, so that: (1) Even when so-called spike-like noise with a large amplitude and a narrow time width is input when no voice is being emitted,
Although the amplitude exceeds the voice detection reference value, since the time width is narrow, the time ratio at which the voice detection reference value is exceeded is smaller than a predetermined ratio, so that no voice detection operation is performed and the magnetic tape will not run erroneously.

(2) When ambient noise is input prior to audio recording, the ambient noise value can be measured by changing the reference value so that the time ratio for which the ambient noise exceeds the reference value matches a predetermined ratio. The reference value of the voice detection means can be automatically set based on the value.

(3) Even if so-called spike-like noise with a large amplitude and a narrow time width is input during recording, the amplitude will exceed the standard value, but the time width is narrow, so the ratio of time that the time width exceeds the standard value is determined in advance. It does not reduce the gain of the microphone amplifier or the recording level by becoming smaller than the ratio.

EXAMPLE An example of the present invention will be described below with reference to the drawings.

FIG. 1 shows the configuration of a tape recorder in one embodiment of the present invention. In FIG. 1, 1 is a microphone for audio recording, 2 is a microphone amplifier, 3 is an A/D converter, 4 is a digital delay means using a semiconductor memory, 5 is an audio detection means, 51 is a comparison means, and 52 is a Reference value, 53 is time ratio measuring means, 54 is comparison means, 55 is reference ratio, 8 is D/
A converter, 7 is a recording circuit, 8 is a recording head, 9 is a magnetic tape, 10 is a control means, 11 is an operating section, and 12 is a tape running mechanism.

The operation of the tape recorder of this embodiment configured as described above will be explained below with reference to FIGS. 1, 2, and 3. 2 and 3 are operational waveform diagrams in the embodiment of FIG. 1.

First, the setting of the voice detection reference value will be explained.

When the operation unit 11 is set to the voice detection reference value setting mode (not shown) in a state where no voice is being input to the microphone 1, ambient noise is being input to the microphone 1 at that time.
The noise is amplified by microphone amplifier 2, and A/D converter 3
The voice becomes digital, and the comparing means 61 of the voice detecting means 5
for a certain period of time (T1 period in Figure 2, for example 100 m5
) is compared with a predetermined reference value 52, the time ratio measurement means 53 measures what percentage of the measurement time exceeds the reference value 62, and the comparison means 54 compares it with a reference ratio 55 (for example, 20%). If the comparison is 20% or more, the control means 10 increases the reference value 52 by a certain percentage and compares it with the digital audio again (period T2). This operation is repeated until the time ratio in which the digital audio exceeds the reference value becomes 20% or less (periods T3, T4, and T5). If it falls below 20% for the first time during T5 at this time, then T5
A value obtained by increasing the period reference value by a certain constant value (for example, 8 dB) is set as the voice detection reference value.

In this case, even if there is so-called spike-like noise with a narrow time width and large amplitude in the ambient noise, if the time ratio exceeding the reference value is 20% or less, the noise will be ignored and the spike noise will be used to detect the voice. The reference value will not be set incorrectly.

Next, voice detection will be explained.

When a voice is input to the microphone 1, the voice is amplified by the microphone amplifier 2, converted into digital voice by the A/D converter 3, and inputted to the digital delay means 4. At the same time, the voice is input to the voice detection means 5.
is also entered. The digital audio input to the audio detection means 5 is compared with a reference value 52 set for ambient noise prior to audio recording for a certain period of time (T1 period in FIG. 3, for example 100 m5) by a comparing means 51, and the time ratio measuring means 53
The comparison means 54 measures the percentage of the measurement time in which the time exceeds the reference value 52, and compares it with the reference ratio 55 (for example, 20%). Output. This detection signal is transmitted to the control means 10
is input, and the tape running mechanism 12 starts running the magnetic tape. On the other hand, the signal delayed by a certain period of time (tl, for example, 200 m5) by the digital delay means 4 is converted into analog audio by the D/A converter 6, and then the recording circuit 7, as shown in FIG. It passes through a recording head 8 and is recorded onto a magnetic tape 9.

Since the time ratio in which the audio signal exceeds the reference value 52 during period T7 in FIG. 3 is less than 20%, the audio detection means 5
stops the detection signal, and controls the control means 10 for a certain period of time (t
2, for example 1 second), the tape running mechanism stops and the magnetic tape 9 stops running.

Also, when there is no audio signal as in period T13 in Figure 3,
Even if so-called spike-like noise with an amplitude greater than the voice detection reference value and a narrow time width is input, the amplitude exceeds the voice detection reference value but the time width is narrow, so the proportion of time exceeding the voice detection reference value will be If the ratio becomes smaller than a predetermined ratio, no audio detection operation is performed, and the magnetic tape will not run erroneously.

Next, gain adjustment will be explained.

When a voice is input to the microphone 1, the voice is amplified by the microphone amplifier 2, converted into digital voice by the A/D converter 3, and input to the voice detection means 5. The digital audio input to the audio detection means 5 is compared by the comparison means 51 for a certain period of time using a value smaller than a predetermined maximum value of the dynamic range of the A/D converter (for example, -6 dB) as a reference value, If the time ratio of audio signals exceeding the reference value exceeds, for example, 20%, the control means 10 reduces the gain of the microphone amplifier 2 by a certain percentage (for example, 3 dB), and if it is less than 0%, the control means 10 reduces the gain of the microphone amplifier 2 by a certain percentage. (For example, 3d
B), and if it is within the range of 0 to 20%, the gain of the microphone amplifier 2 is not changed.

Also, if the time ratio of the audio signal exceeding the reference value is, for example, 20
%, the gain of microphone amplifier 2 will be reduced by 3 dB,
If it exceeds 40%, it will be reduced by 8dB, and if it exceeds 60%, it will decrease by 9dB.
To reduce the dB, the so-called attack time is accelerated (conversely, even if the time ratio of the audio signal exceeding the reference value is, for example, 0% or less, the gain of the microphone amplifier 2 is not immediately increased, and the gain is kept below 0% for a certain period of time. It is also easy to slow down the so-called recovery time, which increases the gain after

With the above gain adjustment means, even if so-called spike-like noise with a large amplitude and a narrow time width is momentarily input during recording, if the time ratio exceeding the reference value is 20% or less, the microphone amplifier 2 It does not reduce the gain, nor does it reduce the recording level on the magnetic tape.

In this way, even when the gain of the microphone amplifier 2 is changed, the voice detection means 5 can detect the absolute value of the microphone input value by increasing or decreasing its voice detection reference value by the gain change, and the voice detection operation is performed. will not interfere in any way.

In the above embodiments, the operation of the voice detection means 5 is shown in a block diagram to make the explanation easier to understand, but this operation can of course be easily implemented using microcomputer software.

As described above, according to this embodiment, (1) By providing a voice detection means that detects voice at a time ratio exceeding a reference value, even if spike-like noise is input when no voice is being emitted, it will cause noise. There will be no false positives.

(2) By providing a configuration in which ambient noise is measured prior to recording and a reference value for the voice detection means is set based on that value, manual sensitivity adjustment is not required.

(3) By providing a configuration that controls the gain of the microphone amplifier at a time ratio exceeding the reference value, the gain of the amplifier will not be reduced even if spike-like noise is input during recording.

Effects of the Invention As described above, the present invention has the following features: (1) A digital audio signal obtained by A/D conversion of an audio signal is compared with a predetermined reference value for a certain period of time, and a time ratio of the digital audio signal exceeding the reference value is determined in advance. a voice detection means for detecting voice by comparing the digital voice signal with the digital voice signal; and a memory means for temporarily storing the digital voice signal.
The digital audio signal read out from the memory means is
By providing a tape running mechanism that converts A and records it on the magnetic tape, even if spike-like noise is input when no sound is being emitted, the noise will not be mistakenly detected as an audio signal, and tape running malfunctions will be prevented. (2) Prior to audio recording, the digital signal obtained by A/D converting the microphone amplifier output during the period when no audio is being emitted is compared with a certain reference value for a certain period of time, and the time ratio of the digital signal exceeding the reference value is determined in advance. By providing a configuration in which the reference value is changed to a predetermined ratio and the audio detection reference value of the audio detection means is set based on the reference value when the ratio matches the predetermined ratio, manual operation prior to recording is eliminated. No need to adjust detection sensitivity; (3) Compare the digital signal obtained by A/D converting the microphone amplifier output with a predetermined reference value for a certain period of time, and compare the time ratio of the digital signal exceeding the reference value with the predetermined ratio. Therefore, by providing a configuration for controlling the gain of the microphone amplifier, even if spike-like noise is input during recording, the gain of the amplifier is reduced and the recording level does not drop, which has a great practical effect.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a tape recorder according to an eleventh embodiment of the present invention, and FIGS. 2 and 3 are operational waveform diagrams of the same embodiment.
FIG. 4 is a block diagram of a conventional tape recorder, and FIG. 5 is a waveform diagram of the same operation. 1...Microphone, 2...Mic amplifier, 3...
A/D converter, 4... digital delay means, 5...
・Voice detection means, 51... comparison means, 52.
...Reference value, 53...Time ratio measuring means, 5
4... Comparison means, 55... Reference ratio, 6.
...D/A converter, 7...recording circuit, 8...recording head, 9...magnetic tape, 10...
Control means, 11... Operating unit, 12... Tape running mechanism. Name of agent: Patent attorney Shigetaka Awano

Claims (3)

[Claims] (1) A microphone that converts audio into an electrical signal, a microphone amplifier that amplifies the electrical signal, an A/D converter that converts the output of the microphone amplifier into a digital audio signal, and a predetermined reference value for the digital audio signal. Compare with for a certain period of time,
a sound detection means for detecting sound by comparing a time ratio of a digital sound signal exceeding a reference value with a predetermined ratio; a memory means for temporarily storing the digital sound signal; and a digital sound read out from the memory means. a D/A converter that converts the signal into an analog audio signal;
A tape recorder comprising: a tape running mechanism that is controlled by the audio detecting means and records the D/A converted analog audio signal on a magnetic tape. (2) Prior to voice recording, the digital signal obtained by A/D converting the microphone amplifier output during the period when no voice is being emitted is compared with a certain reference value for a certain period of time, and the time ratio of the digital signal exceeding the reference value is a predetermined ratio. 2. The tape according to claim 1, wherein the tape is configured to change the reference value so that the ratio becomes equal to 0, and to set the audio detection reference value of the audio detection means based on the reference value when the ratio matches a predetermined ratio. recorder. (3) By comparing the digital signal obtained by A/D converting the microphone amplifier output with a predetermined reference value for a certain period of time, and comparing the time ratio of the digital signal exceeding the reference value with the predetermined ratio, the gain of the microphone amplifier can be determined. 2. The tape recorder according to claim 1, further comprising a configuration for controlling.