Lewis L. Spence
When waves are propagated in a material, the disturbance allows temporary displacement in portions of the material as the disturbance continues from point to point through the medium. A measure of the length of this temporary displacement is called the wavelength. The wavelength is the distance from the crest of one wave to the next or from one trough of one wave to the next.
The frequency, f, is the number of vibrations or oscillation per second occurring in the material. The unit of measurement is Hertz (Hz). One thousand Hertz is called one kilohertz (kHz)
Period, ( (Greek, tau) is the measure of the time for one oscillation. Since the frequency tells how many oscillations occur in one second, and the period tells the time for one oscillation, one could find the value of the other if the value of one of the features is known. For example: if the frequency is 200Hz, that is 200 oscillations in one second, then the period, the time for one oscillation would be 1/200 = 0.02 seconds. Likewise, if the period, (, is 0.01second, the frequency would be 1/0.01 = 100 Hertz.
We could determine the speed or the velocity of the wave. Since speed is the distance divided by the time, which can be classified as rate. In this instance, the rate is the velocity of the sound, c = ( /(, where ( (lambda) is the wavelength. However, since 1/( = f, the velocity can be expressed as c = (f.
The velocity of sound in air is constant, 1100 ft/sec. Therefore it makes it fairly easy to determine the wavelength of a sound wave if the frequency is known. Since the velocity (1100 ft/sec) is constant which is the product of the wavelength and the frequency, it argues that if the value of the frequency is large, the value of the wavelength must be small. If the value of one is double the value of the other is halved. For example, if the frequency is1100 Hz, then the wavelength would be 1 ft. If the wavelength is doubled, 2200 Hz, then the wavelength is 0.5 ft. It will be the same effect on the frequency if the wavelength were doubled or halved.
The ear is the organ in humans which perceives sound. Reasonable acoustics is somewhat subjective; it depends on individual and cultural norms and standards which are not necessarily permanent but acceptable for the age, time and setting. Sound is actually the result of “an organized disturbance of pressure in the air. The human ear is capable of perceiving sounds which are so weak that they cause the ear drum to displace by less than the size of a hydrogen atom which has a diameter of about a billionth of an inch. Such a faint sound has a pressure disturbance of about a billionth of one atmospheric pressure (which is about 14.7 pounds per square inch or 0.1 MPa). Extremely loud sounds which normally produce pain, have sound pressures of about one thousandth of an atmosphere.
The sound we hear is largely dependent on the frequency. It is this particular feature which determines the pitch or timber. Humans perceive sounds with tones as low as 20 Hz and high pitched as 20,000Hz. This implies that the human ear perceives sounds below the lowest tone on the piano scale which has a tone of 27.5 Hz (the note is A ), and above the highest tone which has a fundamental frequency of 4156 Hz, (the note is C).
