How is sound produced? What is the speed of sound?

A stone thrown into water creates a ripple of water and spreads outwards along the horizontal plane. The characteristics of sound are similar. The mechanical vibration of an object produces sound, although the sound does not travel along one plane, but in all directions (spherical).

The sparse air ripples caused by vibration proceed back and forth with a certain period and are often represented by a sine wave, as shown in Figure 1-1.

The speed of sound propagation in the air is generally calculated as 340m/s. Strictly speaking, the speed of sound is related to temperature and humidity, and the speed of sound varies in different media, so for calculation convenience, the speed of sound in this book is always taken as 340m/s.

Sound waves in the air propagation speed, can be approximated by the following formula. Where, t is the temperature of the air (℃).

C=331.4+0.61t(m/s)

In practical applications, when multiple speakers are used simultaneously in a sound field, often calculate the time difference for delay processing, the distance and time difference is calculated as follows:

Distance ÷ speed of sound x 1000 = time difference (ms)

For example, the speed of sound is 340m / s, the difference between the two speakers 12m time difference is how much?

12-340x1000=35.29(ms)

The time difference of Ims in the sound system is also to be taken seriously, because a difference of lms will bring about a distance difference of 34cm. For example, some sound engineers place pickup microphones inside and outside the bottom drum when picking up the bottom drum, the distance between the two microphones is about 34cm, and then give a 1ms delay to the microphone inside the bottom drum at the digital mixing console, which is to consider the speed of sound and the time difference.

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