Decibel Levels of Common Sounds Because decibels increase exponentially, we only need a scale of less than 200 dB to describe any sound you can think of. Likewise our hearing does not have the same sensitivity at all frequencies. Decibels, on the other hand, are an absolute measurement of sound pressure levels, so there is no subjectivity. 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. The above curves are very much like the frequency response curves of microphones and speakers. When power, current, and voltage are provided, decibels can be calculated. A decibel increase of 10 means that a sound has become 10 times more intense or powerful. The higher the decibel level, the louder the noise. Expressed as a formula, the intensity of a sound in decibels is 10 log 10 ( S1 / S2 ), where. The units used to measure sound are decibels (dB). One decibel (0.1 bel) equals 10 times the common logarithm of the power ratio. Medium loudness doesn't change the perceived pitch very much. decibel (dB), unit for expressing the ratio between two physical quantities, usually amounts of acoustic or electric power, or for measuring the relative loudness of sounds. Low frequencies are perceived to be slightly lower than expected if they are very loud. High frequencies are perceived to be a slightly higher pitch than normal if they are very loud. That means a sound of 20dB is 10 times more intense than a sound of 10dB and a 30dB sound is 100 times more intense. (If the reference sound is a jet plane 30 meters away. But the logarithmic decibel scale goes up in powers of ten: every increase of 10dB on the scale is equivalent to a 10-fold increase in sound intensity (which broadly corresponds with a doubling in loudness). Yes, if the reference level used for decibel scale is above threshold of hearing. According to the chart, a 60 dB sound has an intensity that’s one thousand times that of the 30 dB sound (1,000,000 pW/m 2 compared to 1,000 pW/m 2). 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. Sound level is not the same thing as sound intensity. \( \newcommand\) 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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