Sound waves Definition and 333 Threads

In physics, sound is a vibration that propagates as an acoustic wave, through a transmission medium such as a gas, liquid or solid.
In human physiology and psychology, sound is the reception of such waves and their perception by the brain. Only acoustic waves that have frequencies lying between about 20 Hz and 20 kHz, the audio frequency range, elicit an auditory percept in humans. In air at atmospheric pressure, these represent sound waves with wavelengths of 17 meters (56 ft) to 1.7 centimetres (0.67 in). Sound waves above 20 kHz are known as ultrasound and are not audible to humans. Sound waves below 20 Hz are known as infrasound. Different animal species have varying hearing ranges.

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  1. Blockade

    Can someone explain to me these equations of sound waves?

    I = 1/2 ρ v ω2 A2 I don't know what "I" is nor do I know what "A" is but it has to do with sound waves. May you also please correct me if I am wrong but is: ρ = density of air v = velocity of sound = 343 m/s ω = angular frequency of the sound wave = 2πƒ And also may you please answer what is...
  2. grandpa2390

    What do the sound waves look like after Mach 1?

    I get from pictures that the waves in front of the craft get closer and closer together until at Mach 1 they are on top of each other and boom! but! after that, the sound waves form a cone... what is that? is that the head of each wave being produced behind the previous wave and then blasting...
  3. Const@ntine

    Pot falls down toward a man: How long before we warn him?

    Homework Statement Alright, the problem might be somewhere in the translation, or maybe I'm missing something, but anyway, here it is, word for word: You push a pot from the edge of your balcony, which is d = 20.0 m above the ground. The pot falls towards an unsuspecting man, whose height...
  4. 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...
  5. L

    Pressure variation with sound waves equation

    Homework Statement P(average) for a speaker is 10 W. Gamma is 1.4 (ratio of specific heats), molar mass is 28.8 g/mol, air temperature is 50F, and pressure is 1atm. Find Pmax at 100 I have this equation that gives Intensity = (Pmax^2)/(2*Rho*v) where rho is density, and v is speed of sound...
  6. N

    Reflection and Transmission of acoustic waves at a boundary

    Homework Statement An interface is formed between a block of aluminium (density = ##2.70 \times 10^3 kg/m^3##, speed of sound =##6.40 \times 10^3m/s##) and a block of copper (density = ##8.96 \times 10^3 kg/m^3##, speed of sound =##4.76 \times 10^3m/s##). Longitudinal waves traveling through...
  7. Biker

    Answering Sound Wave Questions

    1) How good our approximations of thinking about waves as a function like sin? 2) The power of a sound wave, I have looked on the internet for derivations and all of them used calculus which is a quite expected thing so I skipped it because I still didnt take integration. However I found a proof...
  8. S

    Hardware that can produce sound waves with frequencs 0-200hz

    i'm doing an experiment to study the effect of sound waves on fire and smoke and would like to know how can i produce sound waves with frequencies varying from 0-200 hz
  9. T

    How Can Electromagnetic Waves Translate into Audio Frequencies?

    Hi! For project in one of my classes, I have to research a super power and a possible scientific explanation of it, showing either why it can or can't happen. I chose a super power of translating people's electro magnetic fields into frequencies, and being able to translate that into...
  10. Clara Chung

    2 Sound waves reflection easy problems

    Homework Statement Refer to the photos, question 21 and 22(the one with a helicopter) Homework Equations Both answers are A The Attempt at a Solution for question 21, if the counts to ten, there are 9 intervals. I divide 20 by 9 and divide it again by 2 and get 1.1s not 0.5s. for question 22...
  11. E

    Sound waves in a 'compressed' liquid

    Hi, I have a general question I was thinking about... So, in a liquid the particles are already very close together and as a result they are, in effect, not compressible. That being said, if we take water, for example, it is possible to compress is slightly. It requires, however, a great deal...
  12. P

    Sound waves and speed of it in different reference frames

    Think at a cop car with a siren that moves with a velocity Vc, it emits a sound with a velocity C Now think about a person that doesn't move, in front of the cop car, shouldn't he register that the speed of the sound emited is Vs= Vc+ C? According to the galileian equations (true for v <<c...
  13. Nile Anderson

    Determining the Wavelength of Sound using Resonance Tube

    Homework Statement [/B]Homework Equations I honestly do not know any relevant equations for this relationship. Well except f=v/2l. The Attempt at a Solution The only thing I could assume that it was was some sort of error , but I cannot find much material on the topic , so I was hoping to get...
  14. P

    Calculating Intensities of Out-of-Phase Sound Waves

    Homework Statement A pair of die-hard sports fans decide to ride their motorcycle to the local game, equipped with identical air horns. While stuck at a stoplight, one rider blasts his horn, emmiting a coninuous sound at a frequency of 10 rads/sec. The second rider waits just the right amount...
  15. DianaHerberg

    B Find 3D Models of Waves | Get Creative with 4D Displays

    I am looking for 3D (or 4D, etc.) images of waves (such as light or sound), but seem to be having difficulty locating such models. Can someone please direct me to this kind of display, or is it not something being currently done?
  16. jerromyjon

    Is there a connection between sound waves and gravity waves?

    I'm curious if there is any relation between sound waves and gravity waves. I don't mean as an analogy. I mean can the speed of sound in matter be derived from the energy of gravity waves.
  17. F

    Derivation of the speed of sound waves equation

    I'm learning about the speed of sound waves through a medium. The derivation is initiated through Impulse=change in linear momentum (I=Δp), then I=ΣFΔt=(Area×Δpressure×Δt) in the x direction The derivation proceeds by replacing the Δpressure with another equation we had derived earlier...
  18. NPB777

    Variation of Frequency of sound underwater

    Hello, I am very much interested to how frequency of sound varies in water. Also, how the frequency varies with temperature and depth? What are the different formulas related to this? Secondly, how can we determine the best frequency of operation? I would be very thankful if anyone could answer...
  19. O

    Do sound waves increase temperature?

    Do sound waves increase the temperature of the medium they are traveling through?
  20. K

    Understand Sound Wave Propagation in Space

    Why does sound waves propagate trough space with areas of lower and higher pressure, why does not pressure just equalize without waves? Thanx for answers.
  21. B

    Sound waves in carbon dioxide -- I think book answer is *wrong*

    Homework Statement Sound waves can be refracted when they travel through balloons filled with different gases. How would the motion of a sound wave be changed if it traveled through a balloon filled with carbon dioxide?BOOK ANSWER "Being more dense than air, the carbon dioxide in the balloon...
  22. N

    Moving vehicles and Doppler Effect

    Homework Statement Here is the problem: http://faculty.kfupm.edu.sa/PHYS/kuhaili/doppler_problem.htm {Mentor's edit: Here's the text copied from the url: A fire engine moving to the right at 40 m/s sounds its horn ( frequency 500 Hz ) at the two vehicles shown in the figure. The car is...
  23. H

    How Does a Bugler Control Frequency with Lip and Air Pressure Adjustments?

    Homework Statement By adjustin her lips correctly and blowing with the proper pressure, a bugler can cause her instrument to produce a sequence of tones, amog which are the following: 440, 660, 880, 1100, . . . Hz --- all without changing the length of the air column. (b) What is the ffective...
  24. P

    Sound Waves - Dropping a coin down a well

    The question is: You drop a coin down a well. After 3.2 seconds you hear the sound of the coin splashing into the water surface below. How far below lies the water surface in the well? After doing all the work the answer comes out to d = 46.0 m. However, when solving for "d" I had to solve a...
  25. M

    Are there exceptions to the rule of speed and energy for waves?

    Today I was presented with dispersion in my introductory physics class. Before this topic was presented we were told of two important rules for waves: 1) The speed of a wave is dependent on the medium in which it travels and 2) the frequency of wave does not change when going from one medium to...
  26. N

    Sounds waves in recorders and octaves

    Hello, I've searched the internet for an answer to this question but cannot find it. Not a homework question, I'm just designing a recorder and don't understand this. A recorder is a fipple flute, meaning that it generates standing sound waves by finger placement over holes that change the...
  27. K

    Sound waves and frequency problem

    Homework Statement A public-address system is usually used in the school assembly to obtain better attention from students. Carry out a study on the factors affecting the audibility of sound. Homework EquationsThe Attempt at a Solution Objective: To study how does the frequency of the sound...
  28. Mnemonic

    Power of Sound Wave at distance

    Homework Statement A sound source is placed at the top of a (h = 121.5m) radio tower. The source has a frequency of 653.8 Hz and an amplitude of 11.4 nm at point A. The air surrounding the tower has a density of 1.32 kgm-3 and sound travels through it with a velocity of 340 ms-1. Point A is...
  29. D

    How to Optimize Sound Reflection with Multiple Types of Reflectors?

    I have 2 types of sound reflectors on the image attached. The angles are not proportional but you should get the idea. The black circle is the source, the black lines are the waves and the red lines are the reflections of the waves emitted by the source. My target is to reflect the sound waves...
  30. L

    Which properties of waves are influenced by the medium?

    Which of the following of a wave can be affected by the medium it travels through? (i) wave crest velocity, (ii) wave frequency, (iii) wavelength
  31. fiddleback

    What does the sound coming from an open column look like?

    I believe I understand what happens inside an air column that is open at both ends when you cause a disruption such as blowing into it. But I am not sure what happens in the space between the air column and your ear. Please let me explain what my current understanding is and tell me if I'm...
  32. A

    Highest frequency of sound waves in a thin aluminium rod

    Homework Statement Estimate the highest possible frequency (in Hertz) and the smallest possible wavelength, of a sound wave in aluminium due to the discrete atomic structure of this material. The mass density, Young's modulus, and atomic weight of aluminium are 2.7x103kg m-3, 6x1010 N m-2, and...
  33. Maged Saeed

    Points of destructive interference of sound waves?

    Homework Statement Two speakers (S1,S2), emitting sound waves of frequency 340Hz and separated by a distance of 3 m, are driven by the same oscillator. A listener starts walking from point A to S2 Along the line that joins A and S2> How many points of destructive interference will be observe...
  34. S

    Sound waves frequency (Hankel functions)

    Homework Statement Let's study harmonic sound waves with frequency ##\omega ##, that is emitted by a long wire. Let's approximate the earth, above which the wire is, with an infinite rigid plate. If the space wasn't limited by the earth, than the velocity potential of the source would be ##\Phi...
  35. P

    How Much Energy Hits Each Eardrum from a 2500W Sound Source 20m Away?

    Homework Statement Standing 20m away from a tower generating 2500W of power how much energy/s hits each of your eardrums? Surface area of eardrum=55mm^2 Assume that the speaker generates sound uniformly in a forward hemisphere. Homework Equations I=P/(4πr^2) r=20m P=2500W The Attempt at a...
  36. W

    Frequency of sound waves from vibrating wire

    Homework Statement The wire has mass 250g and is tied down at both ends. It has a length of 12.50m and a fundamental frequency of 25.0 Hz. It has linear mass density. Sound travels at 344m/s in air. Calculate the frequency of the sound waves produced when the wire vibrates at its fifth...
  37. C

    Calculate Intensity of Sound Waves at 3.0 m from Source

    Homework Statement A small source emits sound waves with a power output 80W. a) find the intensity at a point 3.0m from the source. (0.71W/m) b) find the intensity level at the same point as part a.(118.51) c) at what distance would the intensity be one-fourth as much as of that part (a). i...
  38. oreo

    Where Does the Intensity of Sound Waves Go in Complete Silence?

    If we set two speakers far apart, giving identical sound waves having intensity of threshold of pain, in such a way that at midway between them, there is complete destructive interference. Would there any intensity of sound there in complete silence? If not, then where is "lost" intensity gone...
  39. Z

    Speed of sound in turbulent air?

    If I turn on a standing fan in my room how does the speed of sound change in the fast moving air compared to the still air around it? Would it be relatively faster, slower, or does it depend on the direction in which the fan is blowing?
  40. P

    Sound waves in a closed pipe Problem

    Homework Statement Before I write the question you should know that my maths is all correct in my solution but I must have used the formulas incorrectly (or used the wrong formulas). I can't pinpoint where I've gone wrong or if I have left a formula out (I'm a teacher solving this question for...
  41. Z

    Wave Amplification & Frequency Transformation

    I understand the concepts behind the terms in the title; however, I have a question about how to transform the wave energy itself. I'm working on a science fair project that involves transforming sound energy into electrical energy--I understand this is not a very reasonable method of harvesting...
  42. S

    What Happens When the Tension in a Musical Instrument String is Doubled?

    Hello, I am having a hard time solving this question. Any help is really appreciated. 1. Homework Statement You have designed a new musical instrument of very simple construction. Your design consists of a metal tube with length L and diameter L/10. You have stretched a string of mass per...
  43. Nathanael

    Is the Amplitude of Sound Waves Constant with Distance?

    A quote from a book: At first, I was under the impression that s_m was constant. But shouldn't s_m be inversely proportional to the distance? The book never says this anywhere directly, but it seems to be implied by two other equations (for the intensity) given in the chapter...
  44. F

    What is the concept behind sound waves in my class notes?

    I am going through my professor's notes and I am having a difficult time with his notes on sound waves. class notes: First off, I felt like I understood what simple harmonic motion is, but I don't know what the "simple harmonic oscillator moving through air" is referring to. Second, I do not...
  45. C

    Pressure Variation in Sound Waves

    Homework Statement Write an expression that describes the pressure variation as a function of x and t for the waves in air (0∘C) if the air molecules undergo a maximum displacement equal to the diameter of an oxygen molecule, about 3.0×10^−10m. Assume a sound-wave frequency of 55 Hz. Express...
  46. A

    Sound waves and amplitudes Problem

    1. If there is a sound wave traveling in the air, will the amount of air transported by the wave be proportional to the intensity of the wave? Here is my answer: yes, because as the energy of the wave is related to the square of the amplitude of oscillations, the more energy you have, the more...
  47. Jackson Lee

    How Should We Calculate Sound Wave Superposition Intensity?

    The superposition of sound waves puzzled me. Just like the figure below, when two loudspeakers propagate sound waves from two locations to any other locations. We always calculate final wave's amplitude or intensity via considering something just like phase difference or change of amplitude, but...
  48. K

    Sound waves (node and antinodes)

    Homework Statement for part a , since we know that the sand particles will vibrate will max amplitude at antinode and the displacement of partcles is 0 at node. then , the sand should heap at antinode . why the solution gives the sand heap at nodes? Homework Equations The Attempt...
  49. Z

    What Is the Intensity of Isotropic Sound Waves from a Loudspeaker?

    Homework Statement A loudspeaker emits sound isotropically with a power of 100db. Find the intensity in w/m at a distance of 20 from the source Homework Equations Intensity=power/area, For sound wave... power=ro*a*2pi^2*f^2*v*A^2, and I=2pi^2*ro*f^2*v*A^2. db=10log_10_(I/I_0_)...
  50. A

    The amplitude of sound waves from two nearby speakers

    Homework Statement In the figure below, two speakers S1 and S2 emit sound waves of wavelength 2m, in phase with each other. Let Ap be the amplitude of the resulting wave at point P, and Aq be he amplitude of the resultant wave at point Q. How does Ap compare to Aq? a. Ap<Aq b. Ap=Aq c...
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