Now lets see the fallacy of trying to compare this “funny” decibel scale to the percent scale. It is totally unlike the linear percent scale. Similarly, a sound intensity of 50 dB would be 10,000 times as loud (10 x 10 x 10 x 10) as a sound of 10 dB. Therefore, a sound intensity of 20 dB is not twice as loud as a sound intensity of 10 dB, but is 10 times as loud, and a sound intensity of 30 dB is 100 times as loud as a sound intensity of 10 dB. Furthermore, because the decibel scale is logarithmic, every 10 dB increase in sound intensity is actually a ten-fold increase. We define it as the faintest sound that a young sensitive human ear can hear. This means that 0 dB is not the absence of sound, but is an arbitrary zero. Let’s understand how this decibel scale works and why using a percentage value to describe our hearing losses is so very wrong.įirst we need to understand that a decibel is not a given intensity (loudness) of sound, but rather, it is a ratio of how many times louder (or softer) a sound is than a given reference sound level. We can put a stop to this nonsense right now. It seems health care professionals think we are too stupid to understand much, so they let us believe error rather than teach us the truth. Since doctors and audiologists tend to under-estimate their patient’s ability to understand such things (or they don’t understand it themselves), the erroneous concept of dB = % evolved. If we forget about hearing losses greater than 100 dB (like most people tend to do), we get 0 dB to 100 dB as the usable (dynamic) range of hearing for the average ‘normal’ ear. ![]() To make a scale that makes sense to most people (including us knucklehead audiologists), a different equation is used to convert sound intensity using the Sound Pressure Level (SPL) scale to the Hearing Level (HL) scale that goes from 0 dB HL (normal threshold) to 120 dB HL (pain). To measure sound intensity (the way audiologists measure it) you need to do a mathematical calculation that is so strange that 20 + 20 = 26 dB (SPL). Where did the idea come from that we can measure hearing loss in percentages? Here is how Brad Ingrao, an outstanding audiologist, explained it. When people (ignorantly) talk about having a 50 percent hearing loss they likely mean that they have a 50 dB loss. They are as different as trying to compare apples to elephants! Numbers that appear to be similar have vastly differing meanings. Second, the decibel scale is logarithmic, while the percent scale is linear. Any attempt to do so is just a bunch of meaningless gibberish! ![]() Therefore, you cannot calculate a percentage. In both of these scales there is no limiting maximum value. To calculate a percent you need to know the maximum value possible. First, the decibel scale is open-ended like that of the Richter scale used for measuring earthquake intensities. There are two reasons why you can never equate decibels to percentages. Sound intensities are indeed measured in decibels (dB). You have good reason to be confused because you cannot equate decibels to percentages no matter what anyone tells you. In hindsight the error is ridiculous but I did go from a 101 level understanding to a 400 level course within a few weeks so it's unsurprising that I messed up a fundamental.Question: From time to time, I see people writing, “I have 78% hearing loss in my right ear and 95% in the left.” What does this percent mean? I thought sound was measured in decibels (dB), not percent? If this is the case what percent is 115 dB?-R. I've measured this with a Larson Davis SLM and AUDit software and it works. While I'm not converting a value from one decibel scale to another, I'm applying the same offsets to values in different scales and thus the *effect* to both is the same. I apply -25 dBFS to the dBFS value that drove 70 dBHL during calibration. Let's say I need to play back (a pure tone) at 45 dBHL. ![]() Then, to playback at an arbitrary dBHL as perscribed by ANSI/ISO/OSHA standards, I can find the offset from 70 dBHL and apply the same offset to the value in dBFS that drove 70 dBHL. I can calibrate the device to know which amplitude FS would correspond to 70 dBHL (where it seems all calibration is typically done to block out ambient noise). This doesn't make any sense really and only sort of worked. My problem was that I was mixing up needing an "amplitude" in 0-1 (which can of course be converted to decibels on "full scale" or FS) to set for playback "volume" etc and thus was converting dBHL values to amplitude (which really is "amplitude HL" values) and normalizing by the max dBHL value that the device could output for some specific transducer/earphones. For completeness' sake, I did finally figure this out.
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