Sound Intensity

Key Questions

• Question #afa70

  Decibels (dB) are a measurement of noise levels; the higher the number of decibels, the louder the noise. By comparison, a mosquito's buzz is about 40 decibels, while a jet take-off is about 150 decibels.

  This is a scale of various sounds from very quiet (0dB) to loud (140dB). Now, of course, 140dB, isn't the loudest a sound can get, in fact, the Tunguska Meteor reached decibel levels of a staggering 300 - 315dB! The effects of prolonged exposure to loud sounds, such as a rocket launch or jet take-off can include eardrum rupture or temporary deafness,

  Callum S. · 1 · Sep 30 2014
• Question #4d93e

  The main difference is that, normally, you can physically measure the intensity of sound and you get a value (fixed and the same for everybody). Loudness instead is a quantity that represents the psychological response to a sound (such as pain, discomfort, absence) and depends on both intensity and frequency (and actually on the person that is measuring it)!

  Without going into many details about the intensity measurement (you can find them in every Physics book) you have intensity level measured in decibels, dB, which is a Physical measurement while the Psychological sensation of intensity level (loudness) varies adapting itself to the intensity level in dB; for humans (roughly) you have:

  

  In this graph you can see the white area: the lower boundary corresponds to the minimum of intensity (in dB) that you can hear and you see that it varies and depends on frequency (Threshold of hearing) as the upper one (threshold of Pain) that, however, is more horizontal.
  So you cannot really say: “…my threshold of hearing is x dB”, because it varies according to the frequency and to the person good hearing (probably the threshold for a piano tuner and the one of the singer of the heavy metal band Motorhead will vary…for obvious reasons!).

  hope it helps

  Gió · 2 · Feb 24 2015

• Question #4d93e
• Question #4d942
• Question #afa6c
• Question #afa70
• People with good hearing can perceive sounds as low in level as –8.00 dB at a frequency of 3000 Hz. What is the intensity of this sound in watts per meter squared?
• An 8-hour exposure to a sound intensity level of 90.0 dB may cause hearing damage. What energy in joules falls on a 0.800-cm-diameter eardrum so exposed?
• If the warning tag on a lawn mower states that it produces noise at a level of 91.0 dB, what is this in watts per meter squared?
• An electronic point source emits sound isotropically at a frequency of 5000 Hz and a power of 34 watts. A small microphone has an area of 0.79 cm2 and is located 156 meters from the point source. What would be the sound intensity level at the microphone if the point source doubled its power output?
• A sound wave traveling in 20ºC air has a pressure amplitude of 0.5 Pa. What is the intensity of the wave?
• A siren mounted on the top of towers produces a noise of 120 dB at a distance of 2 meters. Treating the siren as a point particle (ignoring reflection and absorption). What is the sound intensity by an observer 12 m away?
• What is the sound level in dB for a sound whose intensity is 5.0 x 10-6 watts/m2?
• The front row of a concert has a sound level of 120 dB and an IPod produces 100 dB. How many IPods would be needed to produce the same intensity as the front row of the concert?
• What sound intensity corresponds to 92 db?
• What is the intensity of a sound which has a sound level of 35 dB?
• How do humans perceive sound intensity?
• How can sound intensity be controlled?
• Question #d75be
• Calculate the level in decibels for a sound having an intensity of 5.00x10^-4Wm^-2?
• An open pipe has a length of 0.75 m. What would be the length of a closed organ pipe whose third harmonic(n=3) is the same as the fundamental frequency of the open pipe?
• A violinist and a pianist simultaneously sound notes with frequencies of 436Hz and 440 hz,respectively. What beat frequency will the musicians hear?
• Question #897e2
• Question #1ce67
• Question #199a9
• Question #d4159
• Question #dd2a2
• Are W/m^2 and dB both units of sound intensity? What is the difference between them?
• What is the relationship between "loudness" and "sound intensity"?
• Question #d39b2
• Question #02d1f
• Question #2e09c
• What causes overtones to be heard?
• Question #c0c5f
• If the intensity of a sound from one source is 100 times that of another sound, how much more is the decibel level of the louder sound than the softer one?
• What is the difference between a deafening sound and a loud sound?