Otolaryngology

Define Sound Sound is a form of energy that is produced by vibrating objects. A sound wave is made up of compression and rarefaction of molecules of media like solid, liquid or air in which the sound waves travel. Velocity of sound is different in each media. In the air, sound travels at a speed of 1120 feet per second at a temperature of twenty degrees Centigrade. It is faster than this through liquids and much faster through the solid medium. What do you understand by the frequency of sound? It is the number of cycles per second. The unit of frequency of sound is measured in Hertz (Hz). This unit is named after the German scientist, Heinrich Rudolf Hertz. A sound wave of 1000 Hz will indicate 1000 cycles per second. What is complex sound? Give an example It is sound made with more than one frequency. Human voice is example of complex sound. The higher the frequency of sound, the greater will be the pitch. The complex sound has a fundamental frequency which the lowest at which a source vibrates. All frequencies above that particular tone are called overtones. These overtones establish the quality of the timbre of sound. What is a decibel in terms of measurement of sound? A decibel (dB) is measured as one-tenth of a bel unit named after Alexander Graham Bell who invented the telephone. The decibel represents a logarithmic ratio between two sounds – that is the sound being described along with the reference sound. Too many decibels constitute noise which can be defined as an aperiodic complex sound. There are three types of noise levels – White Noise, Narrow Band Noise and Speech Noise. What is the dynamic range of sound? It is the difference between the most comfortable level of sound and the discomfort level which can be measured in terms of decibel loudness. The dynamic range of sound is reduced in patients who have positive recruitment phenomenon in the case of a cochlear type of hearing loss. The sound level meter is the instrument used to measure level of noise and other sounds.