Sound intensity Definition and 117 Threads

Sound intensity, also known as acoustic intensity, is defined as the power carried by sound waves per unit area in a direction perpendicular to that area. The SI unit of intensity, which includes sound intensity, is the watt per square meter (W/m2). One application is the noise measurement of sound intensity in the air at a listener's location as a sound energy quantity.Sound intensity is not the same physical quantity as sound pressure. Human hearing is sensitive to sound pressure which is related to sound intensity. In consumer audio electronics, the level differences are called "intensity" differences, but sound intensity is a specifically defined quantity and cannot be sensed by a simple microphone.
Sound intensity level is a logarithmic expression of sound intensity relative to a reference intensity.

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  1. C

    Sound Intensity- just need someone to check my work

    Sound Intensity-- just need someone to check my work :) Homework Statement While enjoyable, rock concerts can damage people's hearing. In the front row at a rock concert, 5m from the speaker system, the sound intensity is 145 dB. How far back would you have to sit for the sound intensity...
  2. I

    Sound intensity level of a thunder bolt

    Homework Statement Find the sound intensity level of a thunder bolt, if a person is standing 200 m from the spot it hits. The bolt hits the ground vertically and the height of the bolt is 1500 m. The bolt has an electrical current of 20 kA and a voltage of 30 MV. It discharges thrice, each...
  3. M

    Clarifying Sound Intensity and Frequency

    Homework Statement Hi guys can someone clarify something in my text. I have included a screenshot, and marked the area in question. Shouldnt it be that as the point source approaches you the intensity AND frequency increase? (see the pitfall prevention)...
  4. G

    Positions for sound intensity max/mins

    Homework Statement Two loudspeakers are placed 3.00 m apart. They emit 494-Hz sounds, in phase. A microphone is placed 3.20 m distant from a point midway between the two speakers, where an intensity maximum is recorded. (a) How far must the microphone be moved to the right to find the...
  5. G

    Converting sound intensity to dB

    Homework Statement The sound at a concert is measured to be 0.5 W/m^2. How many decibels is this? Homework Equations β = 10ln(I/I_0) I/I_0 = 10^(β/10) The Attempt at a Solution I_0 = 1*10^-12 W/m^2 I = 0.5 W/m^2 Therefore, β = 10ln(0.5/10^-12) β = 269.378 dB However, .5/10^12 = 10^(β/10)...
  6. H

    DB(decibals) and sound Intensity

    Homework Statement How much greater than the intensity of a 1 dB sound is the intensity of a: 2dB sound? 3dB sound? 4dB sound? Homework Equations 10pW/m^2 = 10 dB The Attempt at a Solution Hey guys, this question doesn't have an answer in my textbook i think you have multiply...
  7. D

    Percentage Change in Sound Intensity - Help

    Homework Statement An intensity level change of +2.00 dB corresponds to what percentage change in intensity! Homework Equations B = dB = 10 log (I/Io) The Attempt at a Solution 2.00 dB = 10 log (I/Io) 0.2 = log (I/Io) I/Io = 10e0.2 = 1.585 Assuming Io = 1, then percentage...
  8. D

    Sound Intensity Problem of 3 Machines

    Homework Statement In a factory, 3 machines produce noise with intensity levels of 76 dB, 82 dB, and 85 dB. With all three running, what is the intensity level? Homework Equations B = 10 log (I/Io) The Attempt at a Solution B = 10 log (10e7.6 + 10e8.2 + 10e8.5) I do not know...
  9. O

    What are the steps for reducing sound intensity by 20 decibels?

    Homework Statement A man stands 3m from a siren. How far does he have to move to reduce the intensity level by 20 decibels? Homework Equations Intensity level = 10log(I/Io) the inverse square law The Attempt at a Solution i know the answer is 30m because 10 times the distance drops...
  10. P

    Sound Intensity of a microphone

    a) A microphone has an area of 3.8 cm^2. It receives during a 2.87 s time period a sound energy of 4.2x10-11 J. What is the intensity of the sound? b) Using the intensity in the previous question, what is the variation of pressure in the sound wave if the speed of sound is 343 m/s and the...
  11. T

    What Is the New Sound Intensity Level After a 2000-Fold Increase in Power?

    Homework Statement A sound wave is measured to have a 20-decibel sound intensity level (SIL). And the sound wave power flux (measured in Watts/m2) is then increased by a factor of 2000. What is the new sound level (in decibels) after this factor of 2000 increase in sound power? Homework...
  12. P

    What is the sound intensity level of a jet at 1000 feet?

    Homework Statement A jet traveling overhead at an altitude of 5000 feet produces a sound intensity level of 80 dB. What would the figure be for an eight of 1000 feet? Homework Equations The Attempt at a Solution
  13. C

    How Do Sound Intensities Compare Between a Whisper and a Rock Concert?

    During my lecture we were presented with this problem How much louder is the intensity of sound at a rock concert in comparison with the sound of a whisper, if the two intensity levels (in dB) are 120 and 20, respectively? What my professor said was that the rock concert was 100 dB greater...
  14. T

    How Many Machines Must Be Removed to Meet Workplace Sound Regulations?

    Accoding to US government regulations, the maximum sound intensity levels in the workplace is 90,0 dB. Within one factory, 32 ihdentical machines produce a sound intensity level of 92,0 dB. How many machines must be removed to bring the factory into compliance with the regulation? Possible...
  15. H

    Calculating Sound Intensity Levels for a Baby's Parents

    Homework Statement A baby's mouth is 30 cm from her father's ear and 150 cm from her mother's ear. Compute the difference, in dB, between the sound intensity levels heard by the father and by the mother. Homework Equations Intensity = Power/ Area; power = 1/2 * mass per unit...
  16. N

    Noise measurement-decrease in sound intensity with distance

    I am making a noise level meter, that would trigger an alarm, if the noise level has reached hazardous levels. However, one problem with noise is that it'd intensity decreases with distance, so that the meter would percieve a low sound near the meter and a high sound far away as equal. So does...
  17. G

    How Does Sound Intensity Change with Altitude on a Flat Earth?

    Sound intensity on a "flat earth" Homework Statement Consider a flat Earth with an atmosphere that descreases in density as altitude increases such that rho = rho0e-h/H where rho nought is the density of air at zero altitude and H is a constant known as the "scale height". Assume the bulk...
  18. E

    Intensity of sound wave when given sound intensity level.

    Homework Statement What is the intensity of sound wave with sound intensity level 34 dB? Homework Equations B = (10dB) log (I/Io) B = sound intensity level, I = intensity, Io= 1.0x10^-12 W/m^2 The Attempt at a Solution I figured it would be simply a matter of rearranging...
  19. L

    Trumpet players, sound intensity level

    Homework Statement Five trumpet players have a sound intensity level of 75dB. What would be the sound intensity level of 30 such trumpet players? _______dB Homework Equations Increasing the sound intensity by a factor of 10 results in an increase in perceived loudness by approx. a...
  20. L

    What is the relationship between sound intensity level and power?

    Homework Statement What fraction of the acoustic power of a noise would have to be eliminated to lower its sound intensity level from 90 to 70dB? Homework Equations I = Power/Area B = 10 * log *(I/I0) I0 = 10-12W/m2 The Attempt at a Solution The answer I got for this is that the...
  21. M

    Sound intensity and the hearing distance

    Homework Statement A tiny speaker emits sound with a frequency of 1000Hz evenly on all sides. On a distance of 1m from the loudspeaker is an amplitude variation of the particles of air 0.005 μm. On what distance we can barely hear the sound, if the limit of the audible strength or...
  22. R

    What Is the Distance Ratio Based on Sound Intensity Levels?

    Homework Statement Harry and Sally are sitting on opposite sides of a circus tent when and elephant trumpets a loud blast. If Harry experiences a sound intensity level of 65dB and Sally only 55dB, what is the ratio of the distance between Sally and the elephant to the distance between the...
  23. 1

    Sound intensity using decibel values

    okay so I am having trouble with my sound ISU (independent study unit). Though my teacher said he would help, when i asked he said he cant... what i need to find is the sound intensity for the following decibel values.. a) 100dB b) 55dB now the only relevant equation would be \beta= 10...
  24. H

    Sound Intensity and Distance: Exploring the Limits of Human Hearing

    1. If the human ear can detect sound of an intensity of 10^{-12} given a power source of 50W what is the maximum distance the sound could theoretically be heard 2. I = \frac{P}{A} A = 4\pir^{2} 3. Just used first equation to get the area and from that the radius and therefore...
  25. M

    How Far Can a Bird Watcher Hear a Song Bird's Sound?

    Homework Statement A bird watcher is hoping to add a particular song bird to the list of species she has seen. If a person, only 2.11 m from the bird, hears the sound with an intensity of 2.5 x 10^-6 W/m2, how far could the bird watcher be from the bird and still hear it? Assume no...
  26. R

    Need help w/ problem: Sound intensity and energy

    Homework Statement A fan at a rock concert is 30 from the edge of the stage. The sound intensity level at the edge of the stage is 110 dB. The fan's eardrums have a diameter of 8.4 . How much energy is transferred to each eardrum in one second? (Hint: It may help to asume that the speaker is...
  27. W

    How Loud Are Seven Clarinets Compared to One?

    Homework Statement if one clarinet is playing a note at a sound level of 60 dB, what is the sound intensity of 7 clarinets playing identically at one time? Homework Equations is B=(10dB)log(I/Io) relevant to this? The Attempt at a Solution I just need to be pointed in the right...
  28. X

    Calculating Sound Intensity and Level of a Whisper

    Homework Statement What is the sound intensity of a whisper at a distance of 3.0 m, in W/m^2 ? What is the corresponding sound intensity level in dB? Homework Equations I=P/4*pi*r^2 The Attempt at a Solution I tried looking up what the power of a whisper was and I can't find...
  29. D

    How Is Sound Intensity Calculated at Different Distances from a Trumpet?

    Homework Statement When playing fortissimo (very loudly), a trumpet emits sound energy at a rate of 0.800 W out of a bell (opening) of diameter 12.7 cm. (a) What is the sound intensity level right in front of the trumpet? (b) If the trumpet radiates sound waves uniformly in all...
  30. S

    Thesis Help Sound Intensity Probe.

    Thesis Help! Sound Intensity Probe. My final year thesis is to implement a sound intensity probe in MATLAB using two conventional microphones. Using these microphones, i can make recordings of audio to analyse in MATLAB, with the main aim to locate the sound from the phase information, and to...
  31. H

    Sound Intensity Help: Calculate Intensity & Level at 48m Mic Position

    Homework Statement A concert loudspeaker suspended high off the ground emits 36 W of sound power. A small microphone with a 1.0 cm^2 area is 48m from the speaker. What is the sound intensity at the position of the microphone? What is the sound intensity level at the position of the...
  32. D

    How to calculate sound intensity when given decibels

    Homework Statement When a person wears a hearing aid, the sound intensity level increases by 30.0 dB. By what factor does the sound intensity increase? Homework Equations B = (10 dB) log (Ia/Ib) Ia = sound intensity Ib = threshold of human hearing (1.0 * 10^-12 W/m^2) The...
  33. P

    Question about sound intensity (this should be simple I think)

    A recording engineer works in a soundproofed room that is 36.6 dB quieter than the outside. If the sound intensity in the room is 2.27 x 10-10 W/m2, what is the intensity outside? I'm not sure why I can't figure this one out.. My professor confused me when he talked about this.. Do I use...
  34. J

    Police Car Sound Intensity Change

    Homework Statement A police siren produces a sound whose frequency range from 635Hz to 912Hz. When the police car is 220 meters from from the scene of an accident, the sirens blare at 75dB. How many decibels higher will the sound intensity be when the police car is 55m away? Homework...
  35. K

    How Loud Is a Whisper at 3.5 Meters?

    Homework Statement A. What is the sound intensity of a whisper at a distance of 3.5 m, in W/m2? I know that a whisper is approximately 20 dB and P = 10-10 W/m2. B. What is the corresponding sound intensity level in dB?Homework Equations I = Power/[(4pi)(3.5m)2) dB = 10 log (I/Io). The...
  36. P

    How Much More Intense Is Rock Concert Sound Compared to Jazz Fest?

    Homework Statement the sound intensity level at a rock concert is 115 dB, while that at a jazz fest is 95 dB. By what factor does sound intensity increase? Homework Equations The Attempt at a Solution 115-95= 20 10log(rock/jazz)=20 log(rock/jazz)=2 Rock/Jazz=100
  37. G

    Sound intensity as a function of distance from source

    Homework Statement THe intensity of a sound wave at a fixed distance from a speaker vibrating at 1.24 kHz is .388 W/m^2. Calculate the intensity if the frequency is reduced to 2.64 kHz and the displacement is doubled. used I=.5p(w^2)(A^2)v for the initial and the new intensity. I ended up...
  38. T

    What Is the Sound Intensity Ratio Between a Rock Concert and a Jazz Fest?

    [SOLVED] Sound Intensity Level Ratio Homework Statement The sound intensity level at a rock concert is 110 dB, while that at a jazz fest is 100 dB. Determine the ratio of the sound intensity at the rock concert to that at the jazz fest. Homework Equations B=(10dB) log(I/Io) The...
  39. clope023

    Sound intensity - the threshold of pain

    [SOLVED] sound intensity - the threshold of pain Homework Statement You are investigating the report of a UFO landing in an isolated portion of New Mexico, and encounter a strange object that is radiating sound waves uniformly in all directions. Assume that the sound comes from a point...
  40. J

    Sound Intensity pig calling contest

    Sound Intensity "pig calling contest" In a pig-calling contest, a caller produces a sound with an intensity level of 110db. How many such callers would be required to reach the pain level of 120db? The equation I think I have to use is (db_1 - db_2)=10*log(power_1 / power_2) The...
  41. S

    Solving for Sound Intensity: How Far Away is 75 dB? [SOLVED]

    [SOLVED] Sound Intensity Please help! Homework Statement The sound intensity level 5.0m from a point source is 95 dB. At what distance will it be 75 dB? Homework Equations dB = 10log(I/Io) I = P/4*pi*r^2 The Attempt at a Solution I honestly don't know what to do with this...
  42. M

    Sound Intensity and Human threshold for hearing

    Is it possible to have a negative sound intensity level? A sound that is below the threshold of human hearing has... (A) a negative intensity level (in dB). (B) a negative intensity (in W/m^2 ). (C) an intensity level of zero. (D)an intensity level less than 1 dB , but greater than 0...
  43. V

    Sound intensity at a microphone

    Homework Statement A concert loudspeaker suspended high off the ground emits 28.0W of sound power. A small microphone with a 0.900cm^2 area is 51.0m from the speaker. A) What is I at the microphone? B) How much sound energy impinges on the microphone in J? Homework Equations I = P/A I =...
  44. J

    How Does Playing Alone Affect a Violinist's Sound Intensity Level?

    Homework Statement During a rehearsal, all eight members of the first violin section of an orchestra play a very soft passage. The sound intensity level at a certain point in the concert hall is 32.0 dB. What is the sound intensity level at the same point if only one of the violinists plays...
  45. J

    Calculating Sound Intensity 24 m from a Loudspeaker

    Homework Statement The sound level 24 m from a loudspeaker is 66 dB. What is the rate at which sound energy is produced by the loudspeaker, assuming it to be an isotropic source? ____W Homework Equations ? Something to do with Intensity? The Attempt at a Solution I don't...
  46. B

    How Do You Determine Sound Intensity and Speed of an Enemy Submarine?

    Homework Statement You are the captain of a submarine that is on a secret mission deep inside enemy waters. Suddenly your ship is “pinged” by another sub. You are able to determine that the ping comes from the North, has an intensity level of 86.4 dB, and has a frequency of 7270 Hz. You know...
  47. G

    Sound intensity increase as a result of wave interference?

    Homework Statement You're in an airplan whose two engines are running at 560rpm and 570 rpm. How often do you hear the sound intesity increase as a result of wave interference? Well, i know that the intensity will increase when the wave interference is constructive, but point me in the...
  48. V

    Simple sound intensity difficulty

    According to the text, at a distance of 50 m from a jet engine, the sound intensity is 10 W/m2. This corresponds to a loudness (or an intensity level) of 130 dB. [You should convince yourself that this is true.] If you find the sound too loud and you want to reduce the intensity by a factor of...
  49. M

    Sound intensity is measured on a logarithmic scale

    Help please! Here is the prob and i don't not know where or how to begin. 1.Jose was having a really bad day out on the bike. He should have checked the forecast. First, the wind coming out of nowhere. Must have been a steady 30 mph with gusts up to 50, head on. Then the lightning. First 1...
  50. H

    Sound pressure level and sound intensity level

    Hi all. A very simple question: what is the difference between sound pressure level and sound intensity level? It seems to me that sound presssure level also measure the "energy" since it is p^2, which shall be related to energy... If it is so, it seems that sound pressure level shall be the...
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