basic characteristics of sound signal.
Level and loudness: The amplitude of a sound wave determines its loudness or volume. A larger amplitude means a louder sound, and a smaller amplitude means a softer sound. The loudness of a sound is also determined by the sensitivity of the ear. The human ear is more sensitive to some frequencies than to others. The volume we receive thus depends on both the amplitude of a sound wave and whether its frequency lies in a region where the ear is more or less sensitive. The loudness is a sensation of how strong a sound wave is at a place. It is always a relative term and is a dimensionless quantity. Loudness is measured in decibel (dB). It is given as: L = log(I), here „I‟ is the intensity.
Pitch: Pitch is tone frequency.Pitch is a characteristic of sound by which a correct note can be distinguished from a grave or a flat note. We can identify a female and male voice without seeing them. The term „pitch‟ is often used in music. Pitch depends upon the frequencies of the sound wave. A note has a higher pitch when the frequency is high and a note of low frequency has a low pitch.
Frequency response: The audio spectrum range spans from 20 Hz to 20,000 Hz and can be effectively broken down into seven different frequency bands, with each having a different impact on the total sound.
Fidelity: Fidelity is the quality of faithfulness or loyalty.
Sensitivity: sensitivity It is defined as output in millivolts (or in dB below 1 volt) for the sound pressure of 1 Pa (or 10 microbars) at 1000 Hz. As the normal level of speech provides a sound pressure of I microbar ((or 0.1 Pa), the sensitivity based on this criteria for 1 microbar pressure (or 0.1 Pa) level would be one-tenth the value for 1 Pa pressure.
Selectivity: The human ear is very sensitive to sound intensity. It can detect sound intensity as low as 10 dB below the threshold of hearing. The ear is sensitive, not to the absolute values of intensity, but to the ratios (or dB). The sound power generated by a large orchestra is a fraction of a microwatt at the softest tones and about a thousand milliwatts at the loudest ones. Similarly, speech during whispering is in picowatts, and while shouting, it is several milliwatts. It is not necessary for a sound-reproducing system to produce sound of the same magnitude of power as at the source, but the reproducing system should be capable of handling the maximum and minimum power in the same ratio.