In this manner, a violin makes a sound when the bow makes its strikes vibrate, and a piano sounds a note when a key is struck, because a hammer struck a string and made it vibrate.
Speakers are generally used to reproduce these sounds. They are a membrane connected to an electromagnet; as an electrical current travels in front of and behind the magnet very rapidly, it causes vibrations in the air in front of it, and that vibration is sound! This is how sound waves are produced; they can be represented in a diagram as changes in air pressure (or in the electricity level of the magnet) as a function of time.
A sonogram, on the other hand, depicts sound frequencies as a function of time. It should be noted that a sonogram shows fundamental frequency, on top of which higher frequencies, called harmonics, are superimposed. This is what allows us to distinguish between different sources of sound: low notes have low frequencies, while high notes have higher frequencies.
Sampling rate -Sound quality
• 32 kHz: for digital FM radio (band-limited to 15 kHz)
• 44.1 kHz: for professional audio and compact discs • 48 kHz: for professional digital multitrack recording, and consumer recording equipment (like DAT or MiniDisc)
A computer works with bits, so the number of possible values that the sample could have must be determined. This is done by setting the number of bits on which the sample values are encoded.
• With 8-bit coding, there are 28 (= 256) possible values.
• The sampling rate
• The number of bits in a sample
• The number of channels (one for mono, two for stereo, and four for quadrophonic sound