Sound Characteristics 2 of 3
Earlier this week we stared into a few of the basics of engineering sound by learning some fundamental principles of sounds. We have already covered amplitude, wavelength, and velocity. I’ll now pick up where we left off by going over the next 2 points of sound characteristics. Remember that the characters of sound are:
- Amplitude
- Wavelength
- Velocity
- Frequency
- Phase
- Harmonic
- Envelope
Frequency
When a sound wave starts it goes from normal to a high pressure, then drops back to normal, down to a low pressure, and then back to normal. This is called one cycle. Frequency is how many cycles are completed in one second and is measured in hertz (Hz). The higher pitch a sound has, the higher in frequency it will be in hertz, and 1000 Hz is a kilohertz (kHz). This is where music and science start to connect. If you have a musical tone at 440 Hz and double it to 880, the new tone will be 1 octave higher. Any time you double the frequency, you will increase the tone by 1 octave.
One Cycle
Phase
One cycle of a sound wave call also be measured in degrees. Then beginning of the cycle is 0 degrees, the first peak is 90 degrees, middle of the cycle is 180, the negative peak is 270, and the end of the cycle is a full 360 degrees. Phase shift is where you have two identical waves traveling together, but one of those waves is shifted forward or backwards a number of degrees. The greater the shift in degrees, greater the phase shift. If you here an engineer talking about how something is out of phase, he is talking about 2 signals that are not synchronized. The problem with this is if you have a signal that is 180 degrees out of phase mixed into the same channel, the signals will cancel each other out. This is phase cancellation.
Phase Cancellation
This will be all for this week. I will finish up everything on sound characteristics next week and maybe I’ll move onto something a little more fun like microphones. Just remember that you want to cover as much of sound basics as you can because it will only make you a better audio engineer in the future.
