![]() ![]() However, note that when the AMPLITUDE of a single sound is doubled, its level rises 6 dB. Thus, two 70 dB cars together measure 73 dB under ideal conditions. When two sound sources of equal intensity or power are measured together, their combined intensity level is 3 dB higher than the level of either separately. ![]() The result of this logarithmic basis for the scale is that increasing a sound intensity by a factor of 10 raises its level by 10 dB increasing it by a factor of 100 raises its level by 20 dB by 1,000, 30 dB and so on. (The physicist Alexander Wood once compared this range from loudest to quietest to the energy received from a 50 watt bulb situated in London, ranging from close by to that received by someone in New York.) See: DYNAMIC RANGE. This entire range of intensities can be expressed on a scale of 120 dB. Thus, the intensity level is the comparison of one intensity to another and may be expressed: Intensity level = 10 log 10 (I 1 /I 0 ) (dB)įor instance, the difference between intensities of 10 -8 watts/m 2 and 10 -4 watts/m 2, an actual difference of 10,000 units, can be expressed as a difference of 4 bels or 40 decibels.īecause of the very large range of SOUND INTENSITY which the ear can accommodate, from the loudest (1 watt/m 2 ) to the quietest (10 -12 watts/m 2 ), it is convenient to express these values as a function of powers of 10. The decibel is defined as one tenth of a bel where one bel represents a difference in level between two intensities I 1, I 0 where one is ten times greater than the other. Meanwhile, if you want to learn more about sound pressure waves, sound intensity, and the decibel scale, here’s a really great article.A unit of a logarithmic scale of power or intensity called the power level or intensity level. Next in the series, we’ll examine frequency and pitch. The logarithmic nature of the decibel scale can be tough to wrap your mind around, but it’s important to your understanding of the nature and extent of both hearing loss and hearing protection. Check out this Noise Thermometer (a PDF file), which shows the range of various sounds on the decibel scale. So, a sound that’s 120 dB-a jet engine, for example-is one trillion times the intensity of the smallest sound a human can hear. It’s mind-boggling how quickly the logarithmic scale of decibels goes up from there: 0 dBīasically, for every 10 dB increase, we’re adding a zero to the amount of intensity versus the threshold of hearing. Zero on the decibel scale is the “threshold of human hearing”: it’s the least intense sound a human can detect. To see what this looks like, we need to know where we’re starting. Here, going 10 units up the scale increases the previous number by a factor of 10, not by 10 units. Easy enough, right? However, a logarithmic scale is very different. If you start at zero centimeters and add 10, you’re at 10 centimeters start at 10 centimeters, add 10 more, and you’re at 20 centimeters. Think of a linear scale as a tape measure: going 10 units up the scale gets you 10 units more than where you started. (The Richter scale of earthquake intensity is another example of a logarithmic scale.) We measure sound intensity on a logarithmic base 10 scale, which proceeds in multiples of 10, rather than on a linear scale. Human ears can detect an incredibly wide range of sounds. You’ve certainly heard the word “decibel” more than once but do you know how the decibel scale works? Understanding the decibel scale will give you insight into the degrees of hearing loss, and help when it comes to hearing protection. ![]() Our Hearing Protection Series of blog posts takes an in-depth look at hearing protection. It’s important to protect whatever level of hearing ability you still have. Part 1 in our Hearing Protection Series | See Part 2įor many people with hearing loss, hearing protection is a big deal.
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