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| Factors Affecting the Intensity of Sound |
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| The following are the various factors upon which the intensity and hence, loudness of sound depends. |
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| A musical instrument like a guitar or veena gives louder sound when its string is plucked with a greater force. The intensity is directly proportional to the square of the amplitude of vibration of the source. The loudness which is a logarithmic function of intensity, also increases. |
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| The sound from a larger tuning fork is louder than the sound from a smaller one. The sound from a tuning fork becomes louder when its stem is pressed against a table. A vibrating body with larger area is able to make a larger volume of air to vibrate thus, increasing the intensity and loudness. |
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As proved earlier, the intensity of sound varies inversely as the square of the distance from the source. If two points are at distances d1 and d2
from a point source, then the intensities at these points will be in the
inverse ratio of the squares of the distances i.e.,  |
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| The intensity and hence, the loudness increases with the density of the medium in which sound travels. It has been observed that more effort is to be made to make oneself heard by another in aeroplanes or balloons, while flying at high altitudes as the density of air is less. |
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| The sound of a tuning fork or a vibrating string in air is more intense when placed on a sound box which undergoes forced vibration. |
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| According to equation (1-14), the intensity of sound depends on its velocity. If the wind blows in the direction of the sound, the velocity and hence, the intensity and loudness of sound increases. |
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| Intensity of sound depends on its frequency. The human ear is more sensitive to the middle part of the audible range. Thus, a sound of a frequency in the middle of the audible range will appear to be louder than the sound of a frequency near the extremities of the range, though the two sounds have the same intensity. |
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| For example, consider sounds of frequencies 100Hz and 3000Hz, having the same intensity. The sound of 3000Hz will appear to be louder than the other. |
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