JPS6231856B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an automatic audio signal level adjustment device that can automatically and naturally adjust the audio signal level.

Conventionally, when recording an audio signal at a broadcasting station, recording studio, etc., an action called "level adjustment" is usually required in advance. That is, the person to be recorded (usually the announcer) reads out part of the content to be recorded, and the person recording the recording (usually the mixer) adjusts the recording level accordingly using an adjustment console or the like. The appropriate recording level referred to here requires a level as high as possible within the range that does not exceed the allowable input of the recorder used for recording. Therefore, at the time of official recording after the above preliminary actions,
The person to be recorded is required to read out loud at the same level as during the pre-act and at a uniform level from beginning to end.
This requires considerable skill. Even a well-trained announcer may not be able to meet this requirement, and a particular problem arises when the person to be recorded reads out loud at a higher level than the level at which the person was performing the pre-action. In this case, if the recording level exceeds the allowable input level of the recorder, a highly distorted signal will be generated, severely reducing the quality of the recorded content. Conventionally, when such a situation occurs, the recorder would detect the excessive level and lower the recording level using an adjustment console, etc., but it is necessary to detect the arrival of excessive input in advance. In this sense, it is necessary to rely on a high level of skill and a certain kind of intuition, and if the recording level cannot be lowered in time to respond to sudden excessive input, re-recording is required. Nakatsuta. In this way, conventional audio signal recording requires an act called "level matching," which requires skill from both the recorder and the person being recorded, and even then, there are cases where re-recording is necessary. There was a problem with that point.

The present invention improves the above-mentioned drawbacks of the conventional technology, and makes it possible to always keep the recording level within an appropriate range by detecting the arrival of excessive input in advance and automatically lowering the output level. .

The basic configuration of the device of the present invention is shown in FIG. The audio signal input from the signal input terminal 1 is level-controlled by the level control circuit 5 via the delay circuit 3.
The signal is guided to the signal output end 6. Level control circuit 5 is controlled by a signal from level comparison circuit 4. The level comparison circuit 4 compares the level of the input signal from the signal input terminal 1 with the set level from the allowable input setting terminal 2. That is, the level comparison circuit 4 determines whether the signal input exceeds a set level, and if it does, the signal is attenuated by the level control circuit 5 to be kept within an allowable input range. At this time, since the signal input itself is delayed via the delay circuit 3, the level control is performed before the signal exceeding the allowable input level, and a situation where the level control is not completed in time does not occur. It should be noted that this level control must be gradually reduced because abrupt attenuation will cause unnatural phenomena. The contents of the above operation will be explained with reference to FIGS. 2A to 2E.
Now, as an example, consider a case where an audio signal "Ai ew o" is input, and one sound "e" in the audio signal exceeds the permissible setting level. FIG. 2A shows the change in the signal input level over time. This input signal passes through the delay circuit 3 shown in FIG. 1, thereby giving a delay time T, as shown in FIG. 2B. Further, the input signal is compared in magnitude with the allowable input level, that is, the level applied to the allowable input setting terminal 2 in FIG. 1, in the level comparison circuit 4 shown in FIG. 1, and when the allowable input is exceeded, a voltage a is output. . This situation is shown in Figure 2C.
Shown below. In other words, the arrival of an input exceeding the allowable level is detected at time _T1 , but since the signal itself is given a delay time of T in the delay circuit 3, the actual arrival of the excessive input is at ( _T1 +T). Therefore, the level control circuit 5 of FIG. 1 may gradually attenuate the input signal so that it falls within the allowable input range during the time T. This situation is shown in FIG. 2D. That is, from time _T1 , the amplification factor of the level control circuit 5 is gradually decreased from OdB, and at time ( _T1 +T), the amplification factor becomes -NdB. Through this level control circuit, the signal finally led to the signal output terminal, ie, 6 in FIG. 1, becomes as shown in FIG. 2E. As a result, when the device of the present invention is not used, the "e" in the audio signal "iueo"
However, by using the device of the present invention, all audio signals can be kept within the permissible input range, allowing for natural recording without distortion. It is something.

Here, the delay time T and the attenuation amount NdB in the level control circuit will be considered. First, the delay time T is used to detect in advance the arrival of excessive input, and ideally it is desirably equal to or longer than the time required for all recorded contents. However, considering the circuit scale, etc., this is not very practical, so in reality, it is best to attenuate the excessively input sound from about one tone before, as this will have the least influence on other sounds. In normal audio signals, the average length of one note is
The delay time is about 150 msec, and since the most important part for distinguishing an audio signal is the first part of the audio, it is better to set the delay time to about 100 msec. As a result, the level is gradually attenuated from the middle of the sound before the excessively input sound, which causes unnatural effects in addition to making the sound before the sound seem slightly shorter. There's nothing wrong. Next, the amount of attenuation depends on how uniformly the person being recorded reads out loud, but in the case of audio signals, in general, N=
About 6 (dB) is sufficient.

Next, an embodiment of the present invention will be described with reference to FIG. In Figure 3, 1 is the signal input terminal, 2 is the allowable input setting terminal, 6 is the signal output terminal, and 7 is BBD
Delay circuit using (analog type delay element), 8 is
The clock pulse oscillators 9 and 10 which determine the delay time due to BBD are low-pass wave generators for removing clocks, and the delay circuit 3 shown in FIG. 4 is a level comparison circuit using an analog voltage comparison element, 11 is a voltage control amplifier (VCA), and a control terminal 12
The amplification factor is controlled by the DC voltage applied to the Reference numeral 13 denotes a control signal generation circuit that generates a DC voltage for controlling the voltage-controlled amplifier 11. The level control circuit 5 shown in FIG. The above configuration automatically adjusts the level and operates as shown in FIG.

The device of the present invention has the above-mentioned configuration and automatically adjusts the recording level within a certain appropriate level range when recording audio signals, which conventionally required a high level of skill from both the person recording and the person being recorded. Compared to the conventional method, it does not require such skill and can be easily recorded at an appropriate level. In particular, level attenuation is applied gradually from the middle of the sound before the sound of excessively input audio, so that it is possible to achieve natural, distortion-free high-frequency sound with a simple circuit configuration without affecting the discrimination of the sound before the sound. This enables quality recording. Further, according to the present invention, there is no need for a prior action called "level matching" which was necessary in the past, and the recording work can be simplified.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the basic configuration of the audio signal automatic level adjustment device of the present invention, FIGS. 2 A to E are diagrams explaining the operation of the device of the present invention, and FIG. 3 is a block diagram of an embodiment of the present invention. be. 1...Signal input terminal, 2...Permissible input setting terminal, 3
... Delay circuit, 4 ... Level comparison circuit, 5 ... Level control circuit, 6 ... Signal output terminal, 7 ... Delay circuit, 8 ... Clock pulse oscillator, 9, 10 ...
Low-pass wave generator, 11...voltage controlled amplifier,
12...control terminal, 13...control signal generation circuit.

Claims (1)

[Claims] 1. A delay circuit that delays an audio signal, a level control circuit that controls the level of the delayed audio signal, and a level control circuit that compares the level of the audio signal with a set level and determines whether the audio signal level is the set level. and a level comparison circuit that generates a control signal when the level is greater than the set level, and applies the control signal to the level control circuit to detect a single sound of excessively input audio that is a delayed audio signal and exceeds the set level. An audio signal automatic level adjustment device characterized in that the audio signal level is attenuated from the middle of the previous audio so that the audio signal level falls within an allowable input range. 2. In the audio signal automatic level adjustment device according to claim 1, the delay time of the delay circuit is
Audio signal automatic level adjustment device with 100msec and level control circuit attenuation of 6dB.