20dB 102 times, 30dB 103 times the intensity. It is a logarithmic scale, an increase of 10 corresponds to 10 times the intensity. The DeciBel and Intensity Calculations Video Tutorial explains the equations for calculating intensity and deciBel values and demonstrates their use with five example problems. Likewise our hearing does not have the same sensitivity at all frequencies. The decibel scale is a relative scale, based upon the threshold of hearing I0 10-12 W/m2. ![]() A sound that is 10 times more intense ( 110 -11 W/m 2 ) is assigned a sound level of 10 dB. The threshold of hearing is assigned a sound level of 0 decibels (abbreviated 0 dB) this sound corresponds to an intensity of 110 -12 W/m 2. Each question is accompanied by a diagram of a deciBel scale with markings every 10 dB apart. The scale for measuring intensity is the decibel scale. The X of 'X times more intense' is always some power of 10 - for instance, 10 times, 100 times, 1000 times, etc. Students must determine the deciBel rating of Sound Source B. No microphone has the same sensitivity to all frequencies and no speaker reproduces all frequencies equally well, as we will see in Chapter 18 on electronics. Sound Source B is said to be X times more intense that Sound Source A. The above curves are very much like the frequency response curves of microphones and speakers. Medium loudness doesn't change the perceived pitch very much. The equation for SPL is: SP L (20dB)log p. If the reference level is the threshold of hearing, I 0 1pW m2 I 0 1 p W m 2. where is the intensity of the sound and is the intensity of the reference sound to which your sound is being compared. Low frequencies are perceived to be slightly lower than expected if they are very loud. The equation for sound intensity level (SIL) is: SI L (10dB)log I I 0 S I L ( 10 d B) log I I 0. High frequencies are perceived to be a slightly higher pitch than normal if they are very loud. It is also the case that intensity has an effect on perceived frequency the same laboratory frequency will appear to be a slightly different frequency if the intensity is different. ![]() \( \newcommand\) is due to the tube resonance of the auditory canal (see chapter 12 for tube resonance and chapter 10 for a picture of the auditory canal).
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