What is Sound intensity: Definition and 117 Discussions

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. N

    I Sound pressure and inverse distance law

    Hello, I am confused as to how to think about sound pressure and the distance from a sound source. Let's assume that a sound wave is omnidirectional and propagating away from a source in a sphere. We have the following two equations: Pressure = Force/Area Intensity = Power/Area Many texts...
  2. Lotto

    B If I double sound on my PC, how would the sound intensity increase?

    If I have on my PC let's say sound on 50% and I increase it on 100%, how would the sound intensity change? Would it be twice bigger? But I think that function of sound intensity level dependent on sound percets is a linear function, isn't it? How to explain it? Why is it the linear function?
  3. Krystal111

    Question on sound intensity and dB

    Would we have to use the 3-dB exchange rate? How would we solve this question?
  4. C

    Max velocity of a vibrating loud speaker membrane given sound intensity

    My attempt: p and T allows us to calculate ##Z=402 \frac{kg}{sm^2}## using ## Z=p*\sqrt(\frac{\gamma*M}{R*T})## . The sound intensity level at 10 meters allows us to calculate the intensity at 10 meters to be I=10``````^{-7} W/m^2 using ##50 = 10*log(I/I_0)##. Then, using the formula...
  5. K

    Sound intensity - How to deal with decibels?

    I was looking up the maximal amount of noise allowed by current laws, that one can produce. I found that in my region one can produce sounds of up to 45 dB in the period from 22 pm to 7 am. But, it seems evident that the decibels fall off as we distance ourselves from the source. So shouldn't...
  6. K

    Waves: Calculate the sound intensity from two speakers

    Two similar speakers are connected to a stereo system that emits a signal of frequency 𝑓. However, the signal to speaker B is inverted so that positive voltage becomes negative (but with the same absolute value) and vice versa for negative voltages that become positive. A sound intensity meter...
  7. Cc518

    Calculating τ by knowing I is proportional to A^2

    Homework Statement A vibrating standing wave on a string radiates a sound wave with intensity proportional to the square of the standing-wave amplitude. When a piano key is struck and held down, so that the string continues to vibrate, the sound level decreases by 8.0 dB in 1.0 s. What is the...
  8. D

    How does sound intensity affect the current produced by a mic?

    I measure sound (dB) from a speaker at 0cm and 100cm using a diaphragm microphone. 0cm-100dB, 100cm-30dB diaphragm microphone cinsists of a diaphram, coil and a permanent magnet. the coil is attached to the diaphragm, when a sound wave hits the diaphragm it causes to move back and forth which...
  9. M

    Sound intensity of a thunderbolt

    Homework Statement Find the sound intensity of a thunderbolt 1 km away. What sound intensity (dB) is it 1 km away? The thunderbolt can be heard up to 20 km away. The sound is spherical. The air absorbs nothing. Homework Equations L = 10 \cdot lg(\frac{I_1}{I_0}) \Delta L = 10 \cdot...
  10. A

    Calculation for finding distance with regard to sound intensity

    Homework Statement Two amplifiers can be used to power a sound system. Amplifier 1: Has a fixed power output of 300 W. Amplifier 2: Has a variable power output of between 15 W and 175 W. You may assume that the power output of the amplifier is equal to the power of the sound waves that are...
  11. N

    Sound Intensity Propagation and Sound Waves

    Hello everyone, I'd ask you through an illustration which for me would be more clear to put questions I wrote in the image: Thanks to all! Cheers Luigi
  12. N

    About acoustics physics -- The Wave Equation and diminishing sound intensity

    Hello everyone! :-) Actually I'm starting to understand acoustics physics and I figured actually out about this equation: $$\frac{\partial^2\psi}{\partial t^2}=c^2 \nabla^2 \psi$$ which describes practically about pressure and propagation speed into space and time. I know also this equation...
  13. Const@ntine

    Sound Intensity (Level) - Hearing Aid

    Homework Statement A man is wearing a hearing aid device that increases the frequency of the sounds the human ear can conceive, by 30 db. The device "catches" a sound of frequency f = 50 Hz, and intensity I = 3.00 * 10-11 W/m2. What's the intensity that the man's ear hears? Homework...
  14. Tulio Cesar

    Relation between sound intensity and frequency

    The sound intensity formula is given by: dE/dT*dS. So the variables are energy, related to the amplitude of the wave, area, related to wavefronts distribution on space, and time. So many times I don't see any reference about the relation between frequency and sound intensity, but if time is a...
  15. Ian Baughman

    Calculating Sound Intensity and Pressure Variation at a Distance

    Homework Statement A speaker blares out music with a power of 10 W. Assuming the air has a temperature of 50°F and a pressure of 1 atm, what is the sound intensity level in decibels at a distance of 100m away? What is the maximum pressure variation at that point? What is the distance at which...
  16. H

    Question about Inverse Square law and sound intensity

    Homework Statement For school, I have to make a task about sound intensity and the distance to the sound source. I have to prove that the relation between these two is known as the inverse square law _1/ I_2 = ( _2/_1 )². Does someone know how I can plot the inverse square law or prove that it...
  17. karush

    MHB Sound Intensity & Distance Relationship

    4. Sound intensity is inversely proportional to the square of the distance from the source The further from the source you are, the less intense the sound. Suppose the sound intensity is 20 watts per square meter. (W/m^2) at 8 meters. What is the sound intensity at 4 meters...
  18. F

    Sound Intensity: Reduce by 35 dB, Factor Calculation

    Homework Statement If you install special sound-reflecting windows that reduce the sound intensity level by 35.0 dB , by what factor have you reduced the sound intensity? Homework Equations Δβ=10Log(I/I°) The Attempt at a Solution I°=10^-12 I=I°-35 35=10^1.5440680...
  19. UMath1

    Is My Jazz Band Practice Too Loud? Concerns About Sound Intensity

    I recently read about the recommended amount of exposure time to high sound volumes: http://www.dangerousdecibels.org/education/information-center/decibel-exposure-time-guidelines/. Since I am in the Band at school I was somewhat concerned about if the sound intensity would be too much...
  20. E

    Sound Intensity on a Field (no interference)

    Homework Statement Two loudspeakers on elevated platforms are at opposite ends of a field. Each broadcasts equally in all directions. At the halfway point, the intensity is 74.1dB. What is the sound intensity level at a point one-quarter of the way from one speaker to the other along the line...
  21. Y

    Total sound intensity from sources

    Homework Statement A family ice show is held at an enclosed arena. The skaters perform to music with level 80.0 dB. This is too loud for your baby, who yells at 75.0 dB. (a) What total sound intensity engulfs you? Homework Equations I ∝ A2 The Attempt at a Solution Why did the answer sum...
  22. S

    Frequency of varaiation of sound intensity

    Homework Statement A motorcyclist travel at cnstsant speed of 72km/h along a straight road toward an obesrver standing at the centre of bridge over the road . When the motor cyclist is distant, the obesrver hears a sound of 65hz from the engine of the motorcycle. What would be the frequency...
  23. S

    Factors affecting sound intensity

    Homework Statement the factor affecting sound intensity is amplitude and frequency . why not also the distance from the source (r) , in my opinion, intensity = power/area , so the intensity = power/ 4 pi r ^2 ... so I is inversely proportional to r^2 ... Homework Equations The...
  24. S

    Factors affecting sound intensity

    Homework Statement the factor affecting sound intensity is amplitude and frequency . why not also the distance from the source (r) , in my opinion, intensity = power/area , so the intensity = power/ 4 pi r ^2 ... so I is inversely proportional to r^2 ... Homework Equations The...
  25. F

    Sound intensity and speakers

    Homework Statement Three speakers with the same effect are connected to the same tone generator are placed along the y-axis and sends out sound in equal directions. The distance a and b are in the same magnitude as the wave length of the sound...
  26. K

    How far can your voice carry at 40 dB?

    You are in a park when you spot your friend 100 m away. At what lowest decibel should you shout your greetings so that your friend can just hear you? Assume that your friend has normal hearing. My prof never gave an example of how to do this and I can't figure it out. The correct answer is...
  27. J

    Distance from Source to Reach 180/170 dB Intensity Level

    Not a homework... simple curiosity by trying to know this a bit better in order to learn and understand possible effects of sound to marine mammals auditory systems. In sea water, at distance of 1m from a localized sound source, you measure the intensity level as 237 dB. How far away from the...
  28. A

    Sound intensity and distance

    Homework Statement An alarm clock makes a sound that has intensity 60 dB at a distance of 1 m. What is the sound intensity of 100 such clocks which are all 100m away? (A) 0.6 dB (B) 40 dB (C) 50 dB (D) 60 dB Homework Equations I1/I2 = R2^2/R1^2 The Attempt at a Solution If...
  29. W

    Sound Intensity Peak: Find Time Between Peaks

    Homework Statement One wheel goes at 850 rpm and the other at 780 rpm, and obviously they make a noise. Standing in an enclosed room, you hear the sound intensity increase and then decrease periodically due to wave interference. How long does it take between successive times for the sound...
  30. J

    Intensity v.s. sound intensity

    Here's a question I got on an exam: During a typical workday (eight hours), the average sound intensity arriving at Larry's ear is 1.8 x 10-5 W/m2. If the area of Larry's ear through which the sound passes is 2.1 10-3 m2, what is the total energy entering each of Larry's ears during the...
  31. A

    Is max sound intensity at the displacement node in a standing wave?

    Good afternoon all My question is, when we observe stationary waves, and we know that at a certain point, the sound is maximum, is this the displacement node or the displacement antinode? I have read a few different sources and currently i have encountered both. To me it makes more sense...
  32. F

    Equation to find relative sound intensity with angle from source

    What is the equation to find relative sound intensity from a source when given the angle?
  33. Z

    Grade 11 Sound Intensity Question

    Homework Statement If Phrank's new speakers produce a sound of 90dB at 10m, a) How many decibels would be required for the sound to be one hundred times the intensity? b) How close would Phrank need to stand for the intensity to be at 60dB? Homework Equations β2 - β1 = 10 log...
  34. G

    Sound Intensity and Threshold of hearing

    My textbook says that in the equation β= 10log(I1/I2), I1 in most cases is the threshold of hearing (1.0x10^-12). Just out of curiosity, when is I1 not the threshold of hearing?
  35. B

    Sound intensity and relationship to pressure and displacement

    Homework Statement The sound from a trumpet radiates uniformly in all directions in air with a temperature of 20 degC. At a distance of 4.80m from the trumpet, the sound intensity level is 47.0dB. The frequency is 576Hz. Also knowing speed of sound in air is 344m/s, the density is 1.20kg/m^3...
  36. P

    For what slide extensions will trombone produce max sound intensity?

    Homework Statement A 285Hz sound wave is directed into one end of a trombone slide A microphone is placed at the other end to record the intensity of sound waves that are transmitted through the tube. The straight sides of the slide are 80cm in length and 10cm apart with a semicircular bend...
  37. S

    Sound Intensity Level of Three Objects

    Homework Statement Given that: TI1 + TI2 = 70 dB TI2 + TI3 = 80 dB Find TI1 + TI2 + TI3Homework Equations TI = 10 log (I/Io)The Attempt at a Solution From that two equations, I got: I1.I2 = 10-17 I2.I3 = 10-16 I1.I22.I3 = 10-33 Then stuck...
  38. T

    How Do You Calculate the Sound Intensity of Each Singer in a Choir?

    Homework Statement A choir made up by 100 voices (i.e. 100 singers), during the execution of a song, reaches the sound intensity of 100dB. Assuming that all singers sang with the same intensity, the sound intensity of each singer was...? Homework Equations ΔS=10.log(I/Io) The...
  39. R

    Sound intensity, given frequencies

    Homework Statement The intensity of a sound wave at a fixed dis- tance from a speaker vibrating at 1.31 kHz is 0.894 W/m^2. Determine the intensity if the frequency is increased to 2.33 kHz while a constant dis- placement amplitude is maintained. Answer in units of W/m^2 Homework...
  40. E

    What is the intensity of sound 2?

    Homework Statement Sound 1 has an intensity of 39.0 W/m^2. Sound 2 has an intensity level that is 2.5 dB greater than the intensity level of sound 1. What is the intensity of sound 2? Homework Equations I=energy/area*time β=(10dB) logI/Io Io=10^-12 W/m^2 The Attempt at a Solution...
  41. T

    How Do Distance and Power Affect Sound Intensity Levels?

    Second problem of the day...:blushing: Homework Statement (part 1 of 2) A spherical source radiates sound uniformly in all directions. At a distance of 52 m, the sound intensity level is 46 dB. At what distance from the source is the intensity level 13 dB? Answer in units of m...
  42. majormaaz

    Sound Intensity and Bird Watching

    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 2.35 m from the bird, hears the sound with an intensity of 1.9 10-6 W/m2, how far could the bird watcher be from the bird and still hear it? Assume no reflections or...
  43. N

    Calculate the Sound intensity level

    Homework Statement A jackhammer with a sound power of 10 W is operating in the countryside. Calculate the intensity levels at distances of 2.0 m and 50.0 m from the jackhammer. Calculate the corresponding levels in dB. Homework Equations β = (10dB) log (I/Io) where, β = sound...
  44. G

    Exploring Organ Pipes: Standing Waves and Sound Intensity

    hi could somebody explain to me how organ pipes work? so far, i figured out that there are standing waves in an organ pipe, that are determined by the length and the question of whether there is a closed or open end. but what determines the intensity between these possible frequences(e.g...
  45. J

    Sound intensity level, decibels

    A student typing in a computer cluster generates a sound level of 55 dB. What will the dB level the night before essays are due when there are 30 equally noisy students working in the cluster? dBo = 55 Ihearing = 1E-12 W/m2 Bo = 10log(I/Ihearing) 55 = 10log(I/Ihearing) 55 =...
  46. T

    Change in sound intensity over distance

    Homework Statement You are standing in between two sets of railroad tracks. On one set of tracks a train is initially 200 m away and approaching you with a constant speed of v0 = 11 m/s. On the other set of tracks second train is at the same distance and moving away from you at the same...
  47. A

    Relationship Between Sound Intensity and Power?

    I understand the inverse square relationship between sound intensity (I) and distance (r). There was a misunderstanding in physics class today about the mathematical and theoretical relationship between sound intensity and power according to the equation: I = P/4∏r2 Sound intensity is...
  48. L

    Sound Intensity and Sound Level

    Homework Statement The intensity of the sound from a certain source is measured at two points along a line from the source. The points are separated by 11.8 m, the sound level is 68.10 dB at the first point and 60.31 dB at the second point. How far is the source from the first point? d =...
  49. F

    Sound intensity and distance problem

    Homework Statement Henry and Tom see a flash of lightning and then hear the resulting clap of thunder. Henry measures the sound level of the thunder as 65 dB while Tom, who is 800 m further from the event, measures it as 63 dB. Homework Equations The Attempt at a Solution I_H /...