Features Of Audio Signals

- Jun 15, 2018-

Frequency refers to the number of changes in the signal per second. People's perception of the frequency of sounds is expressed as the pitch of the pitch, which is called pitch in music. The pitch is determined by the frequency ω. The division of music in the midscale is based on the logarithmic coordinates (20×log) of the frequency:

Scale: C D E F G A B

Numbered musical notation symbol: 1 2 3 4 5 6 7

Frequency (Hz): 261 293 330 349 392 440 494

Frequency (logarithm): 48.3 49.3 50.3 50.8 51.8 52.8 53.8

Harmonics and tone:

n×ωO is called the higher harmonic component of ωO and is also called overtone. The timbre is determined by the harmonics that are mixed into the pitch, and the richer the higher harmonics, the brighter and more penetrating the timbre. Different harmonics have different amplitudes An and phase shifts ψn, resulting in a variety of timbre effects.

Amplitude and intensity:

The human ear's resolution of the sound details is only the most sensitive when the intensity is moderate. Human auditory response is logarithmic to strength. The average person can only notice a change in the sound intensity of 3 dB. Subdividing does not make much sense. We use the volume to describe the intensity in decibels (dB=20log). When dealing with audio signals, the absolute intensity can be amplified, but its relative intensity is more meaningful, generally defined by the dynamic range: Dynamic range = 20 × log (maximum signal strength / minimum signal strength) (dB)

Sound bandwidth and frequency band:

Bandwidth, or bandwidth, is the frequency range that describes the composition of a composite signal.



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