the conservation and working of the human ear
Answers
Hearing allows one to identify and recognize objects in the world based on the sound they produce, and hearing makes communication using sound possible. Sound is derived from objects that vibrate producing pressure variations in a sound-transmitting medium, such as air. A pressure wave is propagated outward from the vibrating source. When the pressure wave encounters another object, the vibration can be imparted to that object and the pressure wave will propagate in the medium of the object. The sound wave may also be reflected from the object or it may diffract around the object. Thus, a sound wave propagating outward from a vibrating object can reach the eardrum of a listener causing the eardrum to vibrate and initiate the process of hearing.
Sound waves can be mathematically described in two ways, that is, in two domains. In the time domain, sound is described as a sequence of pressure changes (oscillations) that occur over time. In other words, the time-domain description of a sound wave specifies how the sound pressure increases and decreases over time. In the frequency domain, the spectrum defines sound in terms of the tonal components that make up the sound. A tonal sound has a time-domain description in which sound pressure changes as a regular (sinusoidal) function of time. If one knows the tonal components of sound as defined in the frequency domain, one can calculate the time-domain description of the sound. Using the same analytic tools, the frequency domain representation of a sound can also be calculated from the time-domain description. Thus, the time and frequency domain descriptions of sound are two different ways of measuring the same thing (i.e., the time and frequency domains are functional equivalents). Thus, one can describe sound as temporal fluctuations in pressure, or one can describe sounds in terms of the frequency components that compose the sound.
Largely because tonal (sinusoidal) sounds are the bases of the frequency domain description of sound, a great deal of the study of hearing has dealt with tonal sounds. However, everyday sounds are complex sounds, which are made up of many tonal frequency components. A common complex sound used to study hearing is noise. Noise contains all possible frequency components, and the amplitude of the noise varies randomly over time. A noise is said to be “white noise” if it contains all frequency components each at the same average sound level.
A sound waveform has three basic physical attributes: frequency, amplitude, and temporal variation. Frequency refers to the number of times per second that the vibratory pattern (in the time domain) oscillates. Amplitude refers to sound pressure. There are many aspects to the temporal variation of sound, such as sound duration. Sound pressure is proportional to sound intensity (in units of power or energy), so sound magnitude can be measured in units of pressure, power, and energy. The common measure of sound level is the decibel (dB), in which the decibel is the logarithm of the ratio of two sound intensities or two sound pressures. Frequency is measured in units of hertz (Hz), cycles per second. Measures of time are expressed in various temporal units or can be translated into phase measured in angular degrees. Below are some definitions of terms and measures used to describe sound.
The eustachian tube, lined with mucous, is a canal that helps to equalize pressure in the middle ear so that the sound waves are transferred properly. Sound enters the outer ear and makes the eardrums vibrate, and the vibrations are passed along the ossicles.kk
