What is Intensity: Definition and 964 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. 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...
  2. A

    Example to make clear the difference between specific intensity and fl

    hello I amm trying to understand the difference between flux and specific intensity of radiation. I understand that one is dependent on distance the other is not, but can you make it more tangible with an example?
  3. Y

    Relation between RAMAN Intensity and Energy of the photon

    Hi all, What is the relation between RAMAN Intensity and Energy of the photon and/or bond stregth and/or bond energy? Is there any equation or sth explain it easily? If you can explain it in a simple way, I will appreciate. Thanks
  4. C

    Intensity of sound wave & energy passes into ear

    Homework Statement Please refer to the image. Question (a). Homework Equations I= P/(4∏r^2) P=E/t The Attempt at a Solution After a few attempts, I found the way to get the answer: (6.3 x 10^-6) x (1.5 x 10^-4) x 60 = 5.67 x 10^-8 But I don't understand why the area of...
  5. M

    Unraveling the Mysteries of Intensity vs Wavelength

    I am really confused about this! So people thought that as wavelength increases for electromagnetic radiation, intensity of radiation increases but this would mean that people would melt if exposed to any radiation higher than visible light. But then they did an experiment and they sketched the...
  6. T

    Band structure and diffraction intensity

    Hello, Is there an established relationship between the diffraction intensity that a sample produces with its band structure? Thanks
  7. R

    Finding Intensity from an Electric Dipole

    The problem: You and your engineering crew are in charge of setting up a wireless telephone network for a village in a mountainous region. The transmitting antenna of one station is an electric dipole antenna located atop a mountain 2.00 km above sea level. There is a nearby mountain that is...
  8. U

    Reflected Intensity from layer of oil

    Homework Statement Homework Equations The Attempt at a Solution For the second part, I got an answer that is indpendent of the index of oil? That woud mean that the answer would be the same as putting it directly through water.. No clue about the third part. For the last part, Not sure...
  9. M

    Intensity and frequency of radio waves

    Hi, I am not a physicists and have been trying to understand some basic concepts about electromagnetic waves in the context of telecommunications. Now, this is what I know so far: the energy of electromagnetic waves is proportional to it's frequency (E = h*f), and basically it's the energy...
  10. R

    How Do You Calculate the Intensity of an Electromagnetic Wave?

    Howdy everyone. 1. Ok, so we have and electromagnetic wave propagating through a vacuum. We know wavelength, and the magnitudes of B in the x and y directions. Also, B=[Bx(i)+By(j)]cos(kz+ωt). That's all the prereq stuff. 2. So Intensity is: <P>/A & (1/2)Bmax^2/Zo I'm def feeling...
  11. M

    What affects the light intensity and light output geometry?

    These are some of the factors I brainstormed that goes into the functionality of a spotlight: 1) Light output of the light source (measured in luminous flux, if I recall correctly) 2) The reflective potential of the reflectors surrounding the light source 3) The geometry of the reflectors...
  12. T

    LED - Measuring light intensity

    what type of circuit would you draw for this? and how would you actually measure the light intensity of an LED. say you had multiple LEDs and you wanted to compare the light intensity of all of them. how would you do this with with circuit?
  13. S

    Luminosity, Intensity and flux

    what is the difference between luminosity, Intensity and flux in particle physics? Some time people use them in similar meanings.
  14. S

    Reynolds Number Regarding Turbulent Intensity

    Hello, I have a question regarding Reynolds numbers. As I understand, the higher a Reynolds number, the more turbulent a flow becomes, with Re>4000 considered turbulent. I have a model where I've calculated a Reynolds number of 10^7, and when going to set my model boundary conditions I'm...
  15. Q

    Diffraction and intensity of fringes

    I'm not sure if I've understood my textbook correctly. Can you tell me if my current understanding is correct: - in a single slit diffraction there's a wide central fringe which is twice as wide as all the other outer fringes - if we had a double slit diffraction instead of a single slit...
  16. A

    Intensity through each power source

    Homework Statement Please help me to solve this type of circuits... I want to find the intensity through each power source and what voltage does the voltmeter indicates. http://iceimg.com/i/f5/1d/2da68fc0a6.png Homework Equations I=I1+I2 The Attempt at a Solution don't know
  17. L

    Intensity of light through N linear polarizers

    Homework Statement What is the intensity of the electric field that can be transmitted through N linear polarizers if the polarization of the initially linear polarized light is to be rotated 90 degrees? Homework Equations I=IoCos^2x The Attempt at a Solution I am seeing like...
  18. B

    Question on the derivation of Intensity

    Homework Statement When deriving the intensity of an electromagnetic wave in my textbook, there was a part I didn't quite get. It's how I = Watts/m^2 becomes I= u c My textbook gave an example of a electromagnetic wave through a cylinder, with cross-section area A. In 1 second it would...
  19. U

    Desciribing intensity of human scream?

    i was trying to verify the '8 years 7 months 6 days' myth/fact that states that you would have you scream for that much time to produce enough energy to warm up a cup of coffee. i assume that an average human screams at 80 dB.if i have to calculate the power,do i have to take the area of mouth...
  20. 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?
  21. JJBladester

    Radiant Intensity vs. Irradiance

    Homework Statement I am having a hard time discerning the difference between radiant intensity and irradiance. I searched PF and found this distinction, but am still confused. Radiance is the power from the source per area into a certain solid angle. Irradiance is the power onto a...
  22. N

    Furnace flame- light intensity

    Hi Guys, A basic oxygen furnace is very large 400 ton vessel that steel is refined in. during the refining process oxygen is blown into the steel. during this process there is a flame at the mouth of the furnace, this is what I am interesting in. during the process the flame changes in size...
  23. 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...
  24. O

    MCQ about intensity of sound waves (formula manipulation)

    Homework Statement Homework Equations The equation that is already given + (maybe) I is proportional to A2f2. The Attempt at a Solution I took the square root of 8, 8 being the Amplitude and I being proportional to the square of A. (I make the constant of proportionality 1)...
  25. M

    MATLAB Calculate Relative intensity noise using laser Rate equations matlab

    Hello Everybody, I'm trying to plot the frequency spectrum of RIN using Matlab. I've the following code function p=rateblock tau_s = 3e-9; N0 = 1e24; A =1e-12; P0 = 1/(A*tau_s); TSPAN = 0:1e-2:10.23;; Y0 =[0 0]; [T,Y] = ODE45(@rate_equation,TSPAN,Y0); subplot(2,1,1)...
  26. M

    Calculate Relative intensity noise using Rate equations

    Hello Everybody, I'm trying to plot the frequency spectrum of RIN using Matlab. I've the following code function p=rateblock tau_s = 3e-9; N0 = 1e24; A =1e-12; P0 = 1/(A*tau_s); TSPAN = 0:1e-2:10.23;; Y0 =[0 0]; [T,Y] = ODE45(@rate_equation,TSPAN,Y0); subplot(2,1,1)...
  27. 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...
  28. M

    Can materials act as a low pass filter for laser beams?

    There are materials which block laser beams (or light globally) or weaken its intensity via shading i.e. a beam must have crossed a specific energy barrier in order to pass this shading where beams with less energy will fade and won't pass. The question is, is there a material or a type of...
  29. W

    Measures of the intensity of electromagnetic radiation

    I've always struggled with the commonly used measures of the intensity of electromagnetic radiation and it's catching up to me lately. Suppose \bar{P}(R,\phi,\theta) is the Poynting vector of an electromagnetic field (in spherical coordinates) with norm...
  30. S

    Why cosmic ray intensity needs correction with pressure?

    Hi guys, I cannot understand why we need to correct cosray intensity with pressure and why the equation that describes the phenomenon is I=Io*exp(-a(Δp))? I want to know the phsyical meaning of this(i assume,experimental) result... Thank you...
  31. G

    Far field intensity distribution

    Homework Statement Describe the far-field intensity distribution if f(x',y') = circ(\frac{\rho}{D}) cos(\frac{k \theta x'}{2} where \rho = \sqrt{x^{2} + y^{2}}. Homework Equations The Fourier transform of the circ function was given to us earlier: \textbf{F} [ circ(\frac{\rho}{D})...
  32. A

    Calculate light intensity after reflection/refraction

    Hi all, I'm playing around with an autocue type of display. So basically, there is an LCD display that reflects light on a piece of plexi, at a 45 degrees angle. I know that the LCD dispay is horizontally polarized, so I can calculate the refraction and reflection coefficients of the...
  33. Saitama

    Intensity by cylindrical light source

    Homework Statement The intensity produced by a long cylindrical light source at a small distance r from the source is proportional to a)\frac{1}{r^2} b)\frac{1}{r^3} c)\frac{1}{r} d)None of these Homework Equations I=\frac{dF}{dω} I is the intensity, dF is the luminous flux of the...
  34. A

    Question on the relationship between intensity of sound, amplitude and 1/r^2

    Homework Statement Suppose sound wave is emitted uniformly in all directions by a speaker. At a distance of 1.1m, the amplitude of it sound is 1.2x10^-8m What is the amplitude of sound at a distance of 1.7m?The Attempt at a Solution What I'm confused is why does the amplitude of sound change...
  35. S

    Intensity from the double slit.

    Homework Statement Laser light of wavelength λ is incident onto a pair of narrow slits of width a and spacing dWrite down an expression for the intensity as a function of angle of the angle measured from the central axis, θ, in the far-*‐fieldHomework Equations The Attempt at a Solution I...
  36. 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...
  37. J

    Using Ampere's Law in finding H (magnetic field intensity)

    Homework Statement Let the regions 0 < z < 0.3 m and 0.7 < z < 1.0 m be conducting slabs carrying uniform current densities of 10 A/m^2 in opposite directions. Find H (the magnetic field intensity) and different z positions. Homework Equations Biot-Sarvot Law: H = ∫ (I dL X r)/ (4∏R2)...
  38. M

    Intensity of different color light & its relation to energy AND Amplitude

    Hi Let's stick to the classical limit. We have 2 monochromatic light waves of same intensity. Let's say one is blue and one is red. Now this means the individual photons of the blue light have more energy(obviously, higher frequency) and the red light photons have lower energy. But since...
  39. A

    Diffraction: Intensity in the double slit situation

    Hello. I have been studying interference and diffraction and one doubt has appeared. When you consider the double slit experiment forgeting the effects of diffraction you get the following equation for intensity I^{}=4I_{0}cos^{2}(\frac{πdsin(θ)}{λ}) where d is the distance between the...
  40. A

    Intensity - Double slit diffraction

    Hello. I have been studying interference and diffraction and one doubt has appeared. When you consider the double slit experiment forgeting the effects of diffraction you get the following equation for intensity I^{}=4I_{0}cos^{2}(\frac{πdsin(θ)}{λ}) where d is the distance between the slits...
  41. Jalo

    Simple circuit problem - Intensity and Difference of electric potential

    Homework Statement a) Is the current between the points A-B and C-D equal? Why? b) Is the difference of potential between the points B-C and A-D equal? Why? Also, a question of my own.. If I = V/R, then when we measure the intensity between A and B shouldn't it be infinite, or at...
  42. A

    Electromagnetics coulombs law and field intensity

    Homework Statement The circular region, ρ < a, z= 0, carries a uniform surface charge density ρ ( subscript s). Find E at P(0,0,h), h > 0. Homework Equations Coulombs law Field of a line charge and field of a sheet charge.The Attempt at a Solution I'm not sure what they are asking for , but my...
  43. D

    Calculating coal CO2 emission intensity (kg CO2 emitted/kWh delivered)

    Hi all, Would really appreciate some help on this problem I can't seem to figure out. Brown coal has an energy content of 15MJ/kg, carbon content 65% by weight, burning in a 30% efficient steam power plant. Calculate the CO2 emission intensity (kg CO2 emitted/kWh delivered).Assume complete...
  44. 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...
  45. 0

    Electric field intensity inside parallel-plate capacitor filled with water

    First, I’d like to say that this is not homework, but my research work. I’ll be very appreciated if someone could help me to address this issue, many thanks in advance. My experimental purpose is to generate uniform electric field inside microchannel by externally-applied electric field...
  46. U

    Electric field intensity 'inside' a wire carrying current

    I am new here and asking question for the first time of course. My question is very simple. Does electric field intensity exist 'inside' a wire carrying current? Please explain the answer.
  47. L

    Means for increasing the intensity of electrical oscillations

    http://www.google.com/patents/US685012?printsec=abstract#v=onepage&q&f=false Is this system used today in electrical transmission? If not why not?
  48. Y

    Relationship between photoluminescence intensity and Absroption Intensity

    I have measured photoluminescence (PL) and light absroption spectra of some transtion metal oxide nanostructures. The PL intensity increases remarkably by decreasing the size of nanostructures. However, the intensity of absorption vary litte. Is there any relationship between the PL intensity...
  49. U

    Single-slit diffraction intensity

    I have looked through my optics textbook and many websites about single-slit diffraction. They all end up deriving an equation that looks something like this: I = I0*(sinc(B))2, where B = (1/2)*k*b*sin(theta), k = wavenumber, b = slit width. I don't know if there's something I'm not...
  50. 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...
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