What is Intensity: Definition and 963 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.

View More On Wikipedia.org
Recent contents Top users
  1. J

    Possible Difference in Light Paths for Coherent Sources at Point P?

    Homework Statement : The diagram represents two coherent light sources emitting light of equal intensity and wavelength. The intensity of the light at point P is zero. Which of the following could be the difference in path length taken by the light in traveling from each source to point P...
  2. 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...
  3. 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...
  4. P

    What is the intensity formula for a spherical sound wave?

    Homework Statement I need the formula of the intensity of a sound wave at distance r from the source. The wave is spherical, and we know \rho, c, the speed of the wave, \omega, the pulsation, and A, the amplitude of the wave. Homework Equations The problem text specifies that intensity is...
  5. E

    Converting Between Light Intensity and Irradiance: How Do They Relate?

    What is the relationship between light intensity and irradiance? How do I convert one to the other?
  6. I

    What is the electric field intensity at point A due to two point charges?

    Homework Statement Find Enet (magnitude and direction) at point A and include a vector diagram. q1 = 2.0x10^-6 C q2 = 6.0x10^-6 C r1 = 2.5x10^-3 m r2 = 1.7x10^-3 m Homework Equations E = Klql/r^2 or E = Kq/r^2 (the first equation just has absolute values around the q for reminder...
  7. V

    Frequency of first intensity maximum for loudspeakers

    Homework Statement Two loudspeakers are set up 4.0 meters apart and are driven in phase by the same amplifier. The listener is located a sufficient distance away so the angle to the listener is approximately the same at each speaker as indicated in the drawing. The speed of sound is 344 m/s...
  8. 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...
  9. V

    Detecting a stars microwave radiation intensity

    Homework Statement A microwave detector is located 0.5m above the surface of a large lake far from the shore. As a star, emitting monochromatic microwave radiation of 21cm wavelength, rises slowly above the horizon, the detector indicates successive maxima and minima in the signal intensity...
  10. D

    How does the wavelength of light affect its intensity?

    hey everyone, Homework Statement I'm doing a sodium and mercury visible light spectroscopy lab at the moment. By using a PMT, I can detect the intensity of photons emitted as a function of wavelength (controlled parameter). I was wondering if anyone knows how the two relate theoretically...
  11. V

    What is the Power Output of the Sun's Electromagnetic Waves?

    Homework Statement The Sun emits electromagnetic waves (including light) equally in all directions. The intensity of the waves at the Earth's upper atmosphere is 1.5 kW/m2. At what rate does the Sun emit electromagnetic waves? (In other words, what is the power output?) The answer is...
  12. S

    Slit diffraction with a beam of spatially distributed intensity

    Homework Statement I have the classic slit-diffraction experiment, where light is incident on two narrow slits on a screen and is diffracted to create a pattern of maxima and minima on the far surface. It is usually assumed that the light incident on the slits is uniform. In practice, the...
  13. E

    Optimizing radius for minimus electric field intensity

    Homework Statement Assume a spherical electrode of radius r1 and a spherical metal tank of radius r2. The electrode is inside the metal tank. The electrode must operate at a voltage V with respect to a tank. The tank is grounded (V=0). Now let's focus on the electric field intensity at the...
  14. K

    How to find intensity in double slit

    1. Homework Statement the two slit of a double slit each have a width of 0.140mm and a distance between centers of 0.840mm. what the approximate intensity of orders m=o to m=6? 2. Homework Equations i want to use the I/Io = (E/Eo)^2 but some book use I = 4Ao^2sin^2...
  15. K

    Sound Intensity of a Whisper?

    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...
  16. K

    Incident Intensity of light transmitted

    An unpolarized beam of light is incident on a group of three polarizing sheets that are lined up so that the characteristic direction of each is rotated by 45 degrees clockwise with respect to the preceding sheet. What is the fraction of the incident intensity Io that is transmitted? a. zero...
  17. A

    How Does Sound Intensity Change with Fewer Firecrackers?

    Homework Statement if two firecrackers produce a sound level of 95 dB when fired simultaneously at a certain place, what will the sound level be if only one is exploded? Homework Equations dB=10 LOG I + 120 The Attempt at a Solution would I use 2I instead of I making an equation...
  18. C

    Intensity of Near-Infrared Spectroscopy Laser

    Homework Statement Light in the near-infrared (close to visible red) can penetrate surprisingly far through human tissue, a fact that is being used to "illuminate" the interior of the brain in a noninvasve technique known as near-infrared spectroscopy (NIRS). In this procedure an optical...
  19. H

    Help with intensity formula for n slits interference

    Homework Statement somebody help me, i have a homework question: obtaining the formula of calculating the intensity of n slits interfenrece. Homework Equations the only source is the formula to calculate the intensity of double split interference: I/Io = (E/Eo)^2, and I = 4Io(cos(pie...
  20. S

    Intensity of polaroids at an angle

    Homework Statement At what angle should the axes of two Polaroids be placed so as to reduce the intensity of the incident unpolarized light by an additional factor (after the first Polaroid cuts it in half) of 7? b) 25? c) 250?Homework Equations The first polaroid decreases the intensity by...
  21. L

    Relative Intensity in Spectra: What Does It Mean?

    Hi everyone, What does the "relative intensity" mean when we talk about spectra? The intensity relative to what, the background? Thank you
  22. T

    How Is the Force of Sunlight Calculated on a Building's Roof?

    Homework Statement After filtering through the atmosphere, the Sun's radiation illuminates Earth's surface with an average intensity of 1.0 kW/m^2. Assuming this radiation strikes the 15-m x 45-m black, flat roof of a building at normal incidence, calculate the average force the radiation...
  23. M

    How to measure the intensity of Infra red

    Hi, Im investigating how infra red is affected in different areas e.g at home, out side, in the dark or in light. To do this i have made a circuit with a photodiode from the company rapid. The problem is that the photodiode is operating as just a switch, saying if the infrared is on or off so i...
  24. T

    Superconducting material has a rating for critical field intensity

    Hi, here is a couple of questions about superconductors Each superconducting material has a rating for critical field intensity. Now, does the field generated by its own current count? And also what is the current superconducting (type II) material with highest current densities achieved...
  25. P

    Background radiation and intensity

    Hi all, Quick question. I'm reading through Stephen Hawking's a brief history of time (interesting even though I can only understand 1/10th of it). During this book he consistently mentions the fact the microwave radiation detected is near uniform in all directions, which is evidence...
  26. S

    Net Electric Field Intensity

    Homework Statement A rod of length l with a uniform charge per unit length lambda is placed a distance d from the origin along the x axis. A similar rod with the same charge is placed along the y axis. Determine the net electric field intensity at the origin.Homework Equations Electric Field...
  27. P

    Light intensity and photosynthetic rate

    I'm doing a report for biology about the relation betweem light intensity and photosynthetic rate. My results showed that as light intensity decreases, so does oxygen production. I said in my discussion that light rays that must travel longer distances will lose energy and appear dimmer than...
  28. L

    How Much Light Intensity Is Needed to Suspend a Sheet of Paper?

    Homework Statement For a science project, you would like to horizontally suspend an 8.5 by 11 inch sheet of black paper in a vertical beam of light whose dimensions exactly match the paper. If the mass of the sheet is 1.0 g, what light intensity will you need? Homework Equations...
  29. A

    Calculating Energy from Intensity: A Super Nova Scenario

    Homework Statement A super nova releases 2.0×1045 J of energy. It is 1500 ly from earth. If you were facing the star in question, and your face was a circle 7 cm in radius, how much energy would reach your face? Homework Equations I=P/A The Attempt at a Solution I used I=P/A to get...
  30. D

    Can the LF351N op-amp accurately measure light intensity in a fish tank?

    Hello everybody, I am trying to measure the light intensity of light going through a plexiglass (U Shaped) in a fish tank using led. I would love to see accurate voltage measurements due to the change in the liquid level. I tried photodetecr transistors; it wasn't accurate at all. I am thinking...
  31. C

    Calculating Sound Intensity & Energy from Loudspeaker

    Homework Statement A concert loudspeaker suspended high off the ground emits 27.0 W of sound power. A small microphone with a 0.700cm^2 area is 55.0 m from the speaker. What is the sound intensity at the position of the microphone? How much sound energy impinges on the microphone...
  32. J

    Photon Intensity & Distance Calculation

    Homework Statement Supopse that a 100 W source radiates light of wavelength 600 nm in all directions and that the eye can detect this light if only 20 photons per second enter a dark adapted eye having a 7 mm diameter pupil. How far from the source can the light be detected under these...
  33. G

    Power and Intensity for a Sound Wave

    The power for a sound wave is give by P = 1/2*p*A*(w*s)^2*v...in which p is density (rho), A is cross-sectional area, w is angular frequency, s is maximum displacement (amplitude), and v is speed of propagation. The intensity is given by P/A...the intensity for a spherical sound wave is...
  34. R

    Increasing Red Light Intensity Without Color Change

    Hi everyone, In a light bulb, as we increase the temperature of the light bulb, the colour produced by the light bulb changes from red to blue ( intensity vs frequency curve shifts to the left). But if i want to have a red bulb with higher intensity ( i.e. brighter red) without...
  35. G

    Radiation intensity and distance?

    Homework Statement A light ray enters the plastic block in the illustration at an angle of 33.0° and then exits the opposite side. The long side of the block has a length of 0.670 m and its index of refraction is 1.70. For how much time is the light ray inside the block...
  36. A

    Relative intensity changing with temperature?

    I am trying to determine the temperature in a discharge lamp. I have the spectrum of that lamp and Nist Atomic Spectra Database. I don't have the pressure in the lamp (can I determine that too? How?). The spectrum that I have has a low resolution (of about 0.3 nm). Can this be done? 1) One...
  37. Q

    Question about intensity and area

    Hi everyone. Firstly, I know that intensity= Power/Area. But this question made me my mind confused. The question shows the sun shining upon the Earth and the soln is: Only the hemisphere facing the Sun receives energy at any moment. power received by Earth = intensity × area of Earth...
  38. J

    Calculating Electric Field Intensity with Two Spherical Shells

    Hi Two spherical shells where the inner has a radius a and the outer a radius of b. The inner has a total charge of -Q whereas the outer shell has a total charge +Q. The question is to calculate the electric field intensity everywhere in space. My question is now, how do I choose the limits...
  39. R

    What is the relationship between F-number and light intensity in camera lenses?

    I've been searching through the internet and some of my optics books, but nowhere was I able to find the derivation of the law for a camera lens, that the intensity of light that comes on the film or chip is proportional to \frac{D^2}{f^2}=N^2, where D is the aperture diameter, f the focal...
  40. P

    Question about sound intensity

    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
  41. E

    Getting E-Field from magnetic field intensity, H

    Homework Statement Given the magnetic field intensity, H, find E. H=\hat{y}6cos(2z)sin((2x10^7)t - 0.1x) Homework Equations \nabla \times E = \frac{- \partial B}{\partial t} The Attempt at a Solution Since we have H, we can use the relationship that \muH = B and then take the...
  42. Z

    Controlling LED Intensity with Light Sensors

    Hi I would like to know if there is a sensor available in the market that would help control the intensity of light given out by a white LED, taking into account the light coming from the surrounding ambient light. As an example I am trying to implement a project in which I would have to control...
  43. L

    A beam of red light has twice the intensity as a second bean of the same color

    Homework Statement A beam of red light has twice the intensity as a second bean of the same color. Calculate the ratio of the amplitude of wave. Homework Equations intensity \propto (amplitude)^2 The Attempt at a Solution 1^{st} \mbox{ beam} = 2I 2^{nd} \mbox{ beam} = I I don't...
  44. Math Jeans

    How Is Light Intensity Transmitted Through a Glass Slab Calculated?

    Homework Statement Show that for normally incident light, the intensity transmmitted through a glass slab with an index of refraction of n is approximately given by: I_T = I_0 \cdot [\frac{4 \cdot n}{(n + 1) ^ 2}]^ 2 Homework Equations Reflected intensity is given by: I_R = I_0...
  45. D

    Light Intensity: Calculating Energy Flux through an Area Element

    [SOLVED] Light Intensity question The light (electromagnetic) output of a bulb is 40 W. How much energy passes through a 40 cm^2 area element aligned perp. to the light rays? I know that I = Power/Area, but I thought that Power = W(aka. energy) /t , and the problem has no reference to time...
  46. L

    Amplitude and intensity of rock concert

    Homework Statement At a rock concert, the engineer decides that the music isn't loud enough. He turns up the amplifiers so that the amplitude of the sound, where you're sitting, increases by 87.0%. By what percentage does the intensity increase? Do not enter unit. Homework Equations...
  47. 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...
  48. G

    How Does Sound Intensity Change with Multiple Instruments?

    Homework Statement The average sound level of a typical musical instrument in a musical group is B dB. WHat is the sound level in Db if 10 instruments are simultaneously playing. answer choices: B'= 10B, 5B, B+5, B+20, B+2, B+10, B+1, 20B, B, or 2B My first thought was that it would...
  49. U

    Fracture Mechanics - Crack Propagation and Stress Intensity Factors

    I am trying to determine the critical crack length of a part using finite element analysis. The software I am using (ABAQUS) has the ability to perform fracture analysis. I model the part, create a crack, and ABAQUS will output the stress intensity factors (modes I, II, and III) and contour...
  50. T

    Sound Intensity Level Ratio

    [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...
Back
Top