Delayer refers to a kind of audio processing equipment used in audio system. Delayer can delay the audio signal passing through it, so some people call it: delayer. Audio delayers are generally used in systems that require a large sound field and require multiple sets of speakers for sound reinforcement. Because in such a system, after the sound is emitted by speakers in different positions, it arrives at the listener’s ears in order, so in order to ensure the consistency of the sound image, increase the readability of the sound, and avoid the turbidity and turbidity of the sound. At the end, it is necessary for us to use a delay device for related processing.
To understand the working principle of the delayer, we must first understand some acoustic principles.
1. Sound production
Sound is produced by vibration, and then spread through the medium (air, liquid, solid). After the human ear receives the sound signal, it is processed by the brain, and we hear the sound.
2. The speed of sound
1) The speed of sound in the air is about 340 meters per second. In the air, temperature affects the speed of sound transmission. The higher the temperature, the faster the speed of sound. For every 1°C increase in temperature, the speed of sound increases by 0.6 meters per second. For example, at 0°C, the speed of sound is 331 m/s, and at 15°C, the speed of sound = 331 + 0.6 × 15 = 340 m/s. Generally, we use 340 m/s as the standard propagation speed of sound in the air.
2) The speed of sound in liquid is faster than that in air, and different liquids have different speeds of sound. The speed of sound in water is about 1450 m/s. When a person walks to the river, the fish by the river will swim away as soon as they hear the sound of human footsteps. This also proves from the side that water can transmit sound.
3) The speed of sound propagation in solids is faster than that in air and liquid. For example, the speed of sound propagation in steel can be as high as 5000 m/s. The reason is that the speed of sound is related to the density of the molecules of the object. For objects with high density, the distance between molecules is relatively small and the interaction is strong, so the propagation speed is fast and the loss is small. For objects with low density, the distance between molecules is large and the interaction is weak, the speed of sound propagation in it is slower, and the loss is also large.
3. The masking effect of sound
1) The loudness of the sound is large and the mask is small. When one sound is 20dB louder than the other, it can be completely masked.
2) At the same loudness, the mid-frequency sound masks the high and low frequencies, because the human ear is more sensitive to mid-frequency hearing.
The treble frequency masks the low frequency sound, because the treble tone has a sense of prominence and it is easy to mask the bass. In the same sound field, if two speakers with the same parameters use the same sound source and the same sound pressure level, the sound of the speaker that is closer to us will mask the sound of the speaker that is far away.
Diagram of the working principle of the delayerThe circuit is shown in the figure above. When working, after pressing S1 and S2, the rectifier power supply charges C2, and the voltage across C2 quickly reaches the power supply voltage value. At the same time, the power supply provides base bias current for the composite tube composed of V1 and V2 through R, so that the composite tube is turned on, the relay K is closed, and its contact K1-1 is closed together with S1 to provide AC power for the electrical appliance RL, and S1 and S2 are loose. RL can still work normally when it is turned on; but after S1 and S2 are released, capacitor C2 discharges through R and the composite tube, so that the composite tube remains on to maintain the normal operation of RL; with the delay of time, the voltage on C2 If it is not enough to maintain the conduction of the composite pipe, K is released, and the power supply on the electrical appliance RL is automatically cut off, thus achieving the purpose of automatic shutdown. The length of the delay time is determined by the time constants of C2 and R. Changing the value of C2 or R can change the length of the delay time (the delay time is about 7 minutes according to the value in the figure). Increase the value of C2 or R, and the delay time If it becomes longer, the time becomes shorter. This kind of circuit is suitable for lights that will go out automatically on the aisle.
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