Properties of sound waves

Sound is mechanical energy that we hear. Sound wave energy, prodused by  the displacement of air molecules. There are three physical atributes: frequency, amplitude and complexity.

Frequency (pitch)

Although sound waves travel at a fixed speed of 1100 feet per second, sound energy varies in wavelength (frequency).  More preciesly, frequency is the number of cycles that a wave completes in a given amount of time. Sound wavee frequencies are measured in cycles per second called hertz(Hz).

One hertz is 1 cycle per second. We perceive as being low in pitch have slower wave frequencies (fewer cycles per second), whereas sound that we perceive as being high pitch have faster wave frequencies (many cycles per second).

Human's hearing range is from about 20 to 20,000Hz. Many animals communicate with sound, which means that their auditory systems are designed to interpret their species typical sounds.

Amplitude (Loudness)

The intensity of sound, usually meassured in decibels(dB). Amplitude roughly corresponds to our perception of loudness. Sound waves vary not only in frequency, causing differences in perceived pitch, but also in strength, or amplitude, causing differences in perceived intensity, or loudness.

Complexity (Timbre)

Most sounds are a mixture of frequencies. The particular mixture determines the sound's timbre, or perceived uniqueness. Timbre provides information about the nature of asound. For example, timbre allows us to distinguish the sound of a piano from that of aviolin playing the same note.
Sounds with a single frequency wave are pure tones, much like what you would get from a tuning fork or pitch pipe, but most sounds mix wave frquencies together in combinations and so are called complex tones.

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