Tagged Questions

Acoustics is the interdisciplinary science that deals with the study of all mechanical waves in gases, liquids, and solids including vibration, sound, ultrasound and infrasound. Applications of acoustics are for instance the audio and noise control industries.

15 views

Why the Doppler Ultrasound beam needs to be looking directly down at a pipe

So I was doing a question about "Doppler Ultrasound" It states that a Doppler ultrasound uses soundwaves at a frequency much higher than what humans can hear. They can me used to measure the speed of ...
8 views

Speed of sound at phase transition — does percolation theory describe it?

I was discussing with a friend whether we expected liquid water or ice to have a higher speed of sound, near freezing; we figured it would be water since it was more dense. It turned out to be ice (by ...
13 views

Frequency range possible from a mechanical music box [on hold]

Here is a small mechanical music box. The tines of a metal comb are tuned to emit a particular frequency when plucked. The material and structural characteristics of the comb, plucking cylinder, ...
840 views

How does a vibraphone produce correct musical tunes?

As you might already know, frequency of musical notes is arranged in a such a way that if, for example, an A note has frequency of $x$, other A note which is placed one octave higher would produce ...
44 views

Harmonic frequencies of a guitar string

I'm studying harmonic frequency at the moment but I'm just a bit confused about something. How are more than one different frequencies able to be produced from plucking a guitar string (fundamental ...
14 views

Sound source localization in cylinder

I am training an animal (let's assume it's a rat) to do sound-source localization in a cylindrical plexiglass chamber that is approximately 30 cm in diameter (see figure). That is, the animal must ...
168 views

Is there a mathematical relation between the volume of a speaker diaphragm and the intensity of sound it produces?

I am trying to find out how speaker cones of different diaphragm volumes will produce a certain intensity of sound. Is there a relation that could be used after the volume of the cone has been found?
129 views

Intensity of a standing sound wave at displacement nodes?

We know $$P = F\cdot v$$ where $v$ is the velocity vector. Since at the "displacement nodes" in a standing sound wave the velocity of the particles is always 0, the Power must be 0 and hence the ...
70 views

In which-pattern does the individual-particles move in a longitudinal wave?

Transverse waves, such as upper-surface of pond-water, or in shaking-rope; the Transverse-Wave can be easily understood and drawn (for different times such as at t second, t + 0.25 second, t+0.5 ...
344 views

What is the exact physics behind sonic levitation

Me and a group of friends decided to choose sonic levitation as our research topic. However, after looking up the theoretical background, we hit a roadblock: (Here is an image of a standing sound ...
27 views

Mathematical Relationship to find number of antinodes/nodes in a standing wave

So I have been learning about closed pipes (nodes at both ends), open pipes (antinodes at both ends) and open/closed pipes (node at one end and antinode on the other). I have also learnt that for a ...
3k views

How does an acoustic guitar amplify its sound?

An essential part of a guitar is its hollow body. Without it, the strings wouldn't be very loud; as far as I know, the purpose of the body is to set up some sort of resonance and make the sound louder....
28 views

Do ten sounds sound twice as loud as loud or four times as loud as just one sound?

Oddly worded question, but here's the problem. So, basically, according to the HyperPhysics website, it takes 10 violins to sound approximate twice as loud as 1 violin. Assuming that they're all in ...
6k views

Why are the harmonics of a piano tone not multiples of the base frequency?

I was trying to figure out which piano keys were being played in an audio recording using spectral analysis, and I noticed that the harmonics are not integer multiple of the base note. What is the ...
23 views

How would I go about calculating the frequency and amplitude of a sound produced by a collision?

How would I go about calculating the sound pressure level, frequency and amplitude of a sound caused by a collision, given the velocities of the two objects colliding, their acceleration, densities, ...
13 views

How to calculate static air temperature

Let's suppose I have an airplane flying at an unpecified altitude and the following data are given: Flight Mach number: $M=0.76M$ Ground speed: $v_{kts}=470kts$ My goal is to estimate the air ...
31 views

Detect original sound waves

I have just presented a project of mine regarding sound recognition using neural networks. I told during the presentation that I decided to only recognize one sound (musical notes coming from a guitar)...
14 views

Do Conch shell horns produce infrasound?

I was just reading an article about some guys at Stanford playing with ancient conch shell horns: http://news.stanford.edu/news/2011/february/conch-acoustic-musicians-020711.html They mention feeling ...
12k views

Sound - what happens with the particles when a wave passes

I'm having some problems in understanding the principles of sound propagation. The wave propagates though air (for example) exerts compression, which is followed by rarefaction. I think I got than ...
3k views

The speed of sound is a single value yet the speed of atoms is distributed over many values. Does the sound wave front smear out?

Sound waves travel with constant speed, but air molecules that transfer action move with different speeds than the ones described by Maxwell distribution. Why does the sound wave not smear out and ...
6k views

Ultrasonic wave through air

I am not a physicist but I am extremely interested in this area. The simple version of my question is: "What is the maximum range of an ultrasonic wave traveling through air?" Now, I know it depends ...
19 views

Ultrasound in hollow tube

Ultrasound in pulse-echo mode (reflection from air-water interface) is used to measure the level in a tank filled with water. Since the level is several meters, a hollow steel tube is used to ...
621 views

Sound as a use to separate molecular structures

Sound can be a destructive force. However, could it be used to separate say the Hydrogen atom from the Oxygen atoms?
126 views

Is there any way to find difference between two same sounds of different people?

I am trying to understand and find a way to distinguish two same sounds of different people by some physics formula, so could you guys help me? OK I'll try to explain my question in this way that, ...
192 views

Hearing background noise from earphone while there isn't any connection

Once my friend told me that he was listening some background noise while his earphones were not plugged in any device. I didn't believe him but 10 minutes ago I experimented the same. I can certainly ...
10k views

Does sound propagate further in freezing weather?

A few days ago I went for a walk in the evening. We're having winter with a little snow and freezing temperatures. We're in a quiet, shallow valley with a train station about 1km from us. I heard a ...
30 views

Low Frequency Wind Chimes

I'm building a public sound sculpture made of tuned aluminum pipes -- think wind chimes that people can play. I want to include lower frequency chimes in the sculpture, but the fundamental frequency ...
96 views

Doppler shift and change in intensity of a sound wave

How are the intensity of a sound wave and the Doppler shift of frequency related togheter? That is, if the source or the observer are in relative motion, how does the intensity change? For a sound ...
103 views

Sound level of organ pipe driven by helium

The sound pressure level of an organ pipe is a function of the gas flow rate delivered to the pipe. Source Would the sound level of an organ pipe driven by helium be lower than that of a pipe driven ...
27 views

Can the intensity of a sound wave in a minimum be greater than intensity in a maximum?

Suppose to have two speakers $A$ and $B$ one in front of the other, producing coherent sound waves with the same frequency $f$ and power $P$. In different positions on the line connecting the speakers ...
103 views

can a really loud sound travel in space?

I heard in a discovery news video that there is one particle every cubic cm in space. So, if i were to vibrate a circular body of say mass $10^7$kg at $10^{22}$Khz, would i be able to hear a sound ...
34 views

Sound wave dissipation near a solid body

In this answer to a Physics.SE question I found the following intriguing comment: Under typical conditions the sound absorption length is quite long, and not that much heat is produced. A more ...
124 views

Why doesn't steady flow of air create sound? [closed]

When one exhales air by twisting the lips appropriately, one does not create enough sound. But when the same amount of air with the same pressure is blown in a flute or whistle, a relatively audible ...
138 views

At what altitude would the air be too thin to carry a sound wave?

A related question When does an aerobraking space craft create a sonic boom? has spawned a couple of answers, but so far no compelling answers. It is a common belief that in space there is no sound,...
22 views

Frequency shift in case of wind and no relative motion between observer and source

I've learned the following things about Doppler effect in the case of sound waves The Doppler effect formula is to be used in the air reference frame (where $v_{sound}=343 m/s$, at room temperature) ...
48 views

Why pressure standing waves have different nodes location with respect to the corresponding displacement waves?

In acoustics the pressure wave has a $\pi/2$ phase difference with the displacement wave. But I do not understand how this leads to a different position of nodes of pressure inside a tube with ...
2k views

Why do you only hear the bass when someone nearby is wearing earphones?

When someone nearby is listening to music through earphones or headphones, usually you can only hear the bass (unless it's really loud where you can hear the singer's voice and the other instruments ...
177 views

Why do we hear better during the night? [duplicate]

At night, we hear weak and far sounds approximately clear, while during the day we cannot. My high school physics teacher was saying that “this is because of interference of sound waves. During the ...
951 views

Why do you hear an acute sound when you rub your shoe on the floor?

Sorry for the silly question, but I've been wondering about this for quite some time. After raining when I get home I rub my shoe's wet outsole on the floor and I hear an extremely acute (high pitch) ...
4k views

Why does sound absorption in oceans depend on the pH?

I was reading "The Sixth Extinction: An Unnatural History", by Elizabeth Kolbert, and there she comments that high level of $CO_{2}$ in the atmosphere lowers the pH of oceans (which makes sense) and, ...
35 views

Beats: frequency of resulting wave vs. beat frequency

The beats frequency heard from the interference of two sound waves with frequencies $f_1$ and $f_2$ is $$\nu=|f_1-f_2|$$ Nevertheless the frequency of the resulting wave is not $\nu$ but the mean ...
30 views

What enclosed geometry amplifies sound the most?

I am going to build a record player. It will read sound electronically but I also want it to be able to project sound mechanically, like a classic record player. So if sound enters a tube, can you ...
121 views

Significance of wave number?

Till now all I know about the wave number is its formula i.e. ${\frac{2\pi}{\lambda}}$. I always wanted to know what it really means. So can anyone please, explain me its physical significance?
21 views

How to Calculate Sound Pressure Levels using Microphone Sensitivity Rating

This is sort of a cross between a computer science and Physics question, but I would be grateful if anyone here could help me. My objective is to calculate the sound pressure level (in dB) of a ...
70 views

Can sound travel in the form of transverse waves?

We all know that sound is a longitudinal wave but in some books, I have found that sound travels in the form of both longitudinal and transverse waves while passing through rocks. Can anybody explain ...
152 views

'Slapping' sound when trains pass each other

I have noticed that when riding in a train travelling at over 100 kmh$^{-1}$, a loud 'slap' can be heard when another train travelling at a similar speed passes in the opposite direction, followed by '...
106 views

Acoustic beats interference vs. path difference interference

I'm trying to understand the differences between two kinds of waves interference. The first one is a time-interference, only due to frequency difference of the two waves with the same amplitude, which ...
43 views

Speed of sound in solid — temperature dependence

Let $v$ denote the speed of sound in a fixed solid, at a fixed temperature $T$. This will depend on properties of the solid (such as the bulk modulus and density). Given an increase in $T$, does $v$ ...