Agenda - 06-27-1983 - Laserfiche WebLink

Browse Search

411 Sound Pressure Level Our ears are sensitive to a wide range of sound pressures . The loudest sounds that we hear without pain have about one Million times more energy than the quietest sounds we hear. Also , ourj, ears are not equally sensitive to all sound pressures -- it takes more energy to 3 produce a noticeable change in a loud sound than it doesl, to produce a noticeable change in a quiet sound . We can reduce the range of sound pressures to which we are sensitive to a more manageable range , and we can account for the nonlinear sensitivity of our ears by introducing the concept of sound pressure level . In acoustics , the term "level" is used to refer to a logarithmic value of the ratio of a sound pressure quantity relative to a reference quantity . Sound pressure level is a measure of sound pressure relative to a reference pressure of 20 micropascals , 0 .0002 microbarp , or 2x105 newtons per square meter . All of these values are equivalent and are in common use . In your work with airport noise , you are goingl to hear a lot 41M about sound pressure level , because it is the sound pressure level to which people respond , pro or con , in their living and working environments . The language of acoustics is full of abbreviations , and there are two for sound pressure level : "SPL" and "L " "SPL" is more Widely used . ; P 1 Decibels Sound pressure levels are measured in decibels (ab reviation: "dB") , just as distance is measured in inches and temperature is measured in degrees . Decibels are used to express the ratio of two quantities in logarithmic terms . The table below shows a comparison of various sound pressures ( measured in microbars) and their; associated sound pressure levels ( expressed in decibels) . 411 5 'FLIPP t "..1