Likewise our hearing does not have the same sensitivity at all frequencies. Some snorers produce soft murmurs akin to a quiet conversation, measuring around 50 to 60 decibels. 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. FEC and Brightline train horns are equally loud about 118 decibels, according to a decibel meter TCPalm staff used while standing about 10 feet from the railroad tracks in downtown Fort Pierce and downtown Stuart. Creating a comparative scale for context: Snoring, with its variable intensity, occupies a unique spot on the decibel scale. The above curves are very much like the frequency response curves of microphones and speakers. A sound 1,000 times more powerful than near total silence is 30 dB. A sound 100 times more powerful than near total silence is 20 dB. It's a logarithmic scale, so a sound 10 times more powerful is 10 dB. Medium loudness doesn't change the perceived pitch very much. On the decibel scale, the smallest audible sound (near total silence) is 0 dB. Low frequencies are perceived to be slightly lower than expected if they are very loud. You must first antilog each number, add or subtract and then log them again in the following way: For example, adding three levels 94.0 + 96.0 + 98. This scale is used particularly in applications where sound travels in water. We cannot simply add two dB measurements together because sound pressure levels in decibels (dB) employ a logarithmic scale. It is based on orders of magnitude, rather than a standard linear scale, so each mark on the decibel scale is the previous mark multiplied by a value. Sound levels are generally expressed in decibels, which are logarithmic and so cannot be manipulated without being converted back to a linear scale. Another decibel scale is also in use, called the sound pressure level, based on the ratio of the pressure amplitude to a reference pressure. High frequencies are perceived to be a slightly higher pitch than normal if they are very loud. Identify common sounds at the levels of 10 dB, 50 dB, and 100 dB. 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. That is to say that the difference from 1dB to 2dB is not equal to the difference between 10dB to 11dB, even though they are both represented by a 1 decibel change. \( \newcommand\) 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). So the first point to make is that decibels are not measured on a linear scale.