What is Sound wave: Definition and 204 Discussions
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.
Homework Statement
What is the wavelength of a 25 Hz sound wave? What is the wavelength of a 4.5 kHz sound wave?
Homework Equations
wavelength = velocity / frequency or λ = v/f
The Attempt at a Solution
I know that I'm supposed to plug the 25 into the equation, but he didn't give...
Homework Statement
A sound wave with frequency 2 MHz is propagating through water and hits a ship hull made out of steel. The effective value (RMS?) of the acoustic pressure in water is 1kPa = P0w.
The acoustic impedance Zw for water is 1.46*106 and for steel Zs it is 4.03*107. The wave...
A violinist places her finger so that the vibrating section of a 1.0g/m string has a length of 30cm, then she draws her bow across it. A listener nearby in a 20 degrees celcius room (speed of sound at this temperature in air is 343 m/s) hears a note with a wavelength of 40 cm. What is the...
Homework Statement
A sound-level meter placed 150 mm from a small sound source records a reading of 45dB. What is the intensity at that point.
Homework Equations
I m using this equation IL = 10 log(I/I.) where I. is the lowest intensity i think which should be 10^-12 W/m^2.
The...
For a sound wave: A car is moving towards a person at 50m/s and toots its horn. Let's say the speed of sound relative to the air is 340m/s. Does the person measure the speed of the sound to be 390m/s or does it remain at 340m/s?
I've just finished some past exam papers and when marking them using the mark scheme something confused me a little
One question said when a fire engine moves away from an observer, the pitch of the siren decreased, why and I chose the wavelength of the sound wave decreases
The mark scheme...
Homework Statement
Given two isotropic point sources of sound \[s_{1}\] and \[s_{2}\]. The sources emit waves in phase at wavelength 0.50m; they are separated by D = 1.75m. If we move a sound detector along a large circle centered at the midpoint between the sources, at how many points do...
Homework Statement
[PLAIN]http://dl.dropbox.com/u/14655573/110218_203248.jpg
Part (1)
The figure shows the output from a pressure monitor mounted at a point along the path taken by a sound wave of a single frequency traveling at 343 m/s through air with a single frequency traveling at...
Homework Statement
Sound is detected when a sound wave causes the eardrum to vibrate. Typically, the diameter of the eardrum is about 8.4mm in humans. When someone speaks to you in a normal tone of voice, the sound intensity at your ear is approximately 1 * 10^-6 W/m^2. How much energy is...
Homework Statement
"A sound wave of 40.0 cm wavelength enters the tube shown below at the source end. What must be the smallest radius r such that a minimum will be heard at the detector end?" (figure attached)Homework Equations
v =\lambdafThe Attempt at a Solution
I don't have any idea how to...
I know, theoretically ultrasound has no upper limit (everything above 20kHz).. However, I was wondering whether on a practical note a maximum exists? I read somewhere that frequencies of the order 10^12 Hz were reached. Would a maximum frequency be based on the mean free path between the...
Homework Statement
The tension in a guitar string is 21% too high. The fundamental frequency will be...
Homework Equations
V=F\lambda=\sqrt{Tension}
The Attempt at a Solution
I know the answer is 10% too high, but not sure how to get there...
If I take the square root of 1.21, I...
Homework Statement
Assume a piano has 100 different notes from the lowest to highest. We go up from note to note by the same frequency ratio, say starting at 20 Hz. Assuming that the lowest frequency excites the basilar membrane, 30 mm long, at its end, and that this represents a quarter of a...
Homework Statement
The speed of sound in air (in meters per second) depends on temperature according to the approximate expression
v = 331.5 + 0.607T
where T is the Celsius temperature. In dry air, the temperature decreases about 1C for every 150m rise in altitude.
a. Assume this...
Homework Statement
The speed of the sound in the air (in meter per second) depends on temperature according to approximate expression
V= 313.5 + 0.607Tc
where Tc is the Celsius temperature. In dry air, the temperature decreases about 1 degree Celsius for every 150M rise in altitude...
Hi all,
As sound travels through air, does the air molecules travel with the same speed as well?
In other words, if sound is traveling in air at 340m/s, does it also then mean that the mean speed of all the affected air molecules is 340m/s?
I personally do not think so. I guess that...
Homework Statement
(a) A thin, taut string tied at both ends and oscillating in its third harmonic has its shape
described by the equation
y(x,t) = 5.60cm (sin[(0.0340 rad/cm)x]sin[(50.0 rad/s)t]),
where the origin is at the left end of the string, the x-axis is along the string and the...
its my exam question.. i am not so sure... but i put it can't because sound is a wave of vibration which it can diffract but not interence... but i don't know.. can sound wave interference?
cheers
Human's throat sends the sound (person's hidden sound wave) namely reads silently the sound person's hidden sound wave's record and playbacking record the hidden sound wave with mic (1) to be possible the body carrying lightweight power supply sound recording and playbacking (small box) (2)...
Homework Statement
The distance between a node and the nearest antinode of a standing sound wave in air is 7.55 m. What is the frequency of this wave? (Use 343 m/s as the speed of sound in air.)
Homework Equations
velocity = wavelength * frequency
The Attempt at a Solution
I...
A source of sound emits 5.0 mW of acoustic power uniformly in all directions.
1. Calculate the intensity of this sound wave 10.0 m from the source.
2. Find the sound level in decibles 10.0 m from the source.
Answers:
1. 4 x 10^-6 W/m^2 ---- I don't know how to get this answer.
2. 66 dB...
Homework Statement
A radar device emits microwaves with a frequency of 3.20e+09 Hz. When the waves are reflected from a van moving directly away from the emitter, the beat frequency between the source wave and the reflected wave is 838 beats per second. What is the speed of the van...
A sound wave produced by a smoke alarm 35.0 m away is heard 0.103 s after having been started by smoke in the air. The frequency of this sound wave is 1.02 103 Hz. Complete the following.
a.Find the speed of this sound wave in air.
b. Find its wavelength and period.
The sound...
Homework Statement
A 120 cm-long steel string with a linear density of 1.2 g/m is under 100 N tension. It is plucked and vibrates at its fundamental frequency.
What is the wavelength of the sound wave that reaches your ear in a 20 \circC room?
Homework Equations
Fundamental...
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...
Let us consider sound (longitudinal) wave
y=A.sin(\omegat-kx)
See attachment for diagram
Consider air column of length \Deltax and cross-sectional area S at distance x from source.
I want to derive the pressure equation of the sound wave using
Bulk modulus, B=-\DeltaP/(\DeltaV/V)...
Let pressure equation of sound wave be
\Deltap=Pocos(\omegat-kx), then
what will be the density equation of the sound wave?
give your answer with proof and proper explanation...(Derive the equation)
Homework Statement
A sinusoidal sound wave is described by the displacement wave function
s(x,t)=(2.00 μm)cos[(15.7 m^(-1) )x-(858 s^(-1) )t]
b) Determine the instantaneous displacement from equilibrium of the elements of air at the position x = 0.050 m at t = 3.00 ms
Homework...
Homework Statement
A sound wave with 40cm wavelength enters a tube at the source end. What must be the smallest radius r such that a minimum is heard at the detector end (picture attached)?
Homework Equations
I am really lost in this problem, but I BELIEVE constructive/destructive wave...
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...
Homework Statement
A sound wave of the form s = sm cos(kx - ωt + φ) travels at 347 m/s through air in a long horizontal tube. At one instant, air molecule A at x = 2.04 m is at its maximum positive displacement of 6.40 nm and air molecule B at x = 2.08 m is at a positive displacement of 2.10...
We did a lab that involved using sound probes that gave us a bunch of data points which we were able to plot into a waveform using excel. However, we have to determine the equation of the waveform and it is expected that we include the uncertainty of the coefficients (much like using the LINEST...
Homework Statement
Two speakers, one directly behind the other and along the x-axis, emit sound waves along the x-axis. The speaker in the back emits sound with a wavelength of .02 m and the speaker in the front emits waves with a wavelength of .05m. If the two speakers are separated by 3 m...
1. A certain instant camera determines the distance to the subject by sending out a sound wave and measuring the time needed for the echo to return to the camera. How long would it take the sound wave to return to the camera if the subject were 3.00 m away?
2. d = vt
3. d = vt...
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...
Homework Statement
A sound wave is incident on a pool of fresh water. The sound enters the water perpendicularly and travels a distance of 0.52 m before striking a 0.18 m thick copper block lying on the bottom. The sound passes through the block, reflects from the bottom surface of the block...
Homework Statement
Well it's not so much a direct question as it is several.
I'm very confused about sound waves. I know that, when modeled as a transverse wave on a set of axis, a compression is a maximum and a rarefaction is a minimum. But where do nodes and antinodes fit into this? Which...
I was just wondering if anyone has any idea on how I would go about working this out. I have performed the experiments at home, placing a container of water on top of a speaker and then playing a high frequency and high dB sound through them, however, I can not find any equations online or in my...
Any kind soul to help me with this questions...i am stuck
qn. The amplitude of vibration of a certain sound wave is increase by 50%. What is the corresponding increase in the decibel level of the sound?
My attempt..
beta= 10 log ( I/Io)
lets just take I = 2.0 x 10^-7
let just take...
I have a closed end tube that is 23.75" in length, .905" in OD and .222" in ID.
What I am trying to do is replicate what is done on an organ flue pipe with an adjustable length collar and try to tune the pipe for a certain frequency.
My collar ID is .905" or .683" larger than the tube's...
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...
Homework Statement
a spherical sound wave source at the origin emits a sound wave with frequency 13100Hz and a wave speed of 346m/s. what is the phase difference in degrees and radians between the two points with (x,y,z) co-ords (1cm,3cm,2cm) and (-1cm,1.5cm,2.5cm)??
Homework Equations...
I played the audio song on my 8 Ohm audio speaker. I used my Computer Audio Port to play the song. I played that song on my speaker, it worked perfectly, but when I invert the audio signal 180' out of phase, the voice generated was the same.
That is to say, when the speaker used to contract, it...
Homework Statement
A rock group is playing in a club. Sound emerging
outdoors from an open door spreads uniformly in
all directions. If the decibel level is 70 dB at a dis-
tance of1.0 m from the door,at what distance is the
music just barely audible to a person with a normal
threshold...
I had today an exam.
I that exam this graph they said represent a sound wave. Is this graph correct representing a sound wave in a medium? My interrogation is about y/m as a function of x/m!
Thanks in advance!
Homework Statement
1. "When filling your car with gasoline, in the last few seconds before filling the tank, a noise with a rising pitch comes from the tank. Explain"
2. "Liona Boyd, a famous Canadian guitarist, tunes her guitar's A string with a 440 Hz tuning fork. Beats are heard at a...
Ok, so recently I've moved on to sound waves in my high school class. I was wondering if sound waves could be harnessed for demolation with accuracy?
I was thinking the sound would have to move in a linear vibrational path, without dispersing (making a cone shape), is this possible?
Homework Statement
Michelle is enjoying a picnic across the valley from a cliff. She is playing music on her radio (assume it to be an isotropic source) and notices an echo from the cliff. She claps her hands and the echo takes 1.2 s to return.
(a) Given that the speed of sound in air is 343...