8
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Will a short brick wall help shield against bass or will it go around?
The wavelength of sound at 40Hz is about 28 feet.
However tall the wall is, the sound will diffract over the top of it and spread downwards on the far side.
If you made the wall about 5 wavelengths ...
- 12.6k
4
votes
Acoustics resonance question
The idealized "open boundary condition" that is given in a first course on sound waves in pipes doesn't exist in the real world. The reason is that the pipe radiates sound into the environment, (...
- 12.6k
4
votes
How much noise does a road noise barrier block?
The US Federal Highway Administration says:
Effective noise barriers can reduce noise levels by 10 to 15 decibels, cutting the loudness of traffic noise in half.
It goes on to say that a 5 dB ...
- 151
4
votes
Why would a "delayed loudspeaker" be so expensive in the 1970s?
The band was the Grateful Dead and the invention necessary was an analog delay line that was inserted between the main audio mix signal line and the power amps that drove the speaker arrays (which ...
- 15.3k
3
votes
Acoustic absorption of different materials? (gypsum board versus plaster)
What you're looking for is called the Acoustic Absorption Coefficient. Which is a measure of how much sound a material absorbs. Unfortunately, it's not as simple as that, mostly because the ...
- 2,145
3
votes
Motor control sounds
Question 1: generally which specific types of component vibrate, and what force causes the vibration (e.g.: capacitors, thyristors, magnetism, etc)?
Most of the sound is going to come from coils - ...
- 11.1k
3
votes
Can two microphones placed within centimeter distance together measure a distance of the sound source?
A sound source and listening device can only provide direction.
Multiple microphones is how passive submarine sonar works. This will give direction only. Note that microphones in a line can only ...
- 7,148
3
votes
Simplest way to reduce low frequency noise from windows
Some thoughts on your problem: have a look at the physics behind "Chladni plates" - your window pane will act as a passive speaker at 166Hz but not in a "pumping" fashion like a ...
- 31
3
votes
Simplest way to reduce low frequency noise from windows
From your troubleshooting it does sound like the window is resonating. Below is a good visualization of one potential vibration mode from the Vibration of plates Wikipedia article. The mode for your ...
- 8,285
3
votes
Accepted
Controlled oscillation of a piano string by electromagnetic, mechanical, or other means
What you describe has been on the market for over 40 years for electric guitar use; it is called an E-Bow. It contains a sense coil, a drive coil, a battery, and an amplifier circuit inside a case you ...
- 15.3k
2
votes
How much does a wall stop sound?
How tall the wall needs to be depends on a few factors as others have mentioned in the comments. Since you've provided relatively vague design criteria, I cannot give a definite answer. However, this ...
- 106
2
votes
Optimal size and shape for a steel target?
From 1,000 yards away the sound will not seem extremely loud, but in the right conditions, should be audible. I would go with 3/8" thickness for durability as well as producing a nice "ping", as well ...
- 21
2
votes
Why aren't these kind of drivers used in loudspeakers?
that thing is indeed an loudspeaker- just a small one. it operates on exactly the same principles as a full-size loudspeaker. because it doesn't take much movement of air in a headphone to fry your ...
- 15.3k
2
votes
Will a 3-wall acoustic barrier work or will sound go around?
For fans used to move air, their primary noise radiation frequency will be (number of blades) x (revs per second of the fan shaft) and will be emitted in all directions if the fan shaft is vertical, ...
- 15.3k
2
votes
Will a 3-wall acoustic barrier work or will sound go around?
It will help to shield you from direct high pitch noise waves. because these waves short wavelengths will be blocked by objects in the range of your partition size.
Say a noise of frequency of
500-...
- 22.8k
2
votes
Is there a technical name for a sound dampening suspended cylinder in loud indoor environments?
I don't know if there is a specific name for that. But it is a known fact that sound-absorbing fabrics and foams especially if placed in acoustical focal points of noisy spaces large enough to promote ...
- 22.8k
2
votes
Accepted
Why is the Cape Elizabeth Fog Signal shaped like this?
The steel structure will be designed as a diffraction grating to create a directional sound beam.
To make a directional sound source, the area covered by the source needs to have linear dimensions ...
- 12.6k
2
votes
Accepted
How can I calculate the total signal level (noise) of PC fans?
This is a pretty straightforward calculator: https://www.engineeringtoolbox.com/adding-decibel-d_63.html
Basically noise level is dictated by your 2 loudest sources, so 50 dB + 40 dB (assuming they ...
- 2,357
2
votes
Will a short brick wall help shield against bass or will it go around?
Short frequency noise will tend to go around and even through objects, soil, or foundations to your home, as base humming sound.
For 40 hertz or wavelengths of 5-10 meter object of the sizes of the ...
- 22.8k
2
votes
Accepted
Will a short brick wall help shield against bass or will it go around?
You may try to build something like highway sound barrier. They say that modified acrylic sheet is the best material for this, and I guess it's cheap.
Other option is not to build wall, but to ...
- 36
2
votes
What is the mechano-acoustic effect of off-centering the black paste on tabla-drum skins?
Simply put, the blobs of paste act to damp out any vibrational modes which would have had mode maxima at that physical location. The energy applied to the drum then goes into other modes, presumably ...
- 4,259
2
votes
Accepted
Confusion over textbook formulae for directional characteristics of sound sources
The sound pressure does go negative, that is out of phase with the reference signal.
Incidentally your plot is confusing to me, as x axis seems to be either frequency or wavelength(?), so you are ...
- 902
2
votes
Effect of bracing on a music instrument top - is FEM modal analysis enough to predict this?
Bracing in the simplest way, say a large flat sheet extended reasonably long in both directions will increase the stiffness of the sheet and hence reduce its natural frequency. This will lead to ...
- 22.8k
2
votes
Accepted
Effect of bracing on a music instrument top - is FEM modal analysis enough to predict this?
What can (and what can't) modal analysis tell me about the transfer of periodic motion from the bridge (where the strings are attached) to the soundboard?
Very often in engineering, we find ourselves ...
- 2,676
1
vote
How do I calculate hourly LAeq sound pressure level using 1-mint LAeq values?
Leq represents the time weighted average. So isn't it just:
$$Leq (hour) = \frac{1}{60}\sum_{n=1}^{60}Leq(minute_{n})$$
- 196
1
vote
Are there materials that are good at transmitting sound but thermally insulating?
In doing a quick scan of Google for your answer, I came across an article on a ring type device developed by scientists at Boston University that passes air but blocks sound in certain frequency ...
- 601
1
vote
Are there materials that are good at transmitting sound but thermally insulating?
From the diagram you have provided us it appears to me that trying to "brute force" a noise cancellation scenario with a single loudspeaker at right angles to the flow of the exhaust gas is highly ...
- 601
1
vote
Elastic waves in very thin plate
I've not looked at your specific equations, but in general if you take a plate and make it very thin, that's called a membrane. A membrane is to a plate what a string is to a beam. It has no bending ...
- 2,676
1
vote
Estimating the quality factor (decay properties) of an object's vibrational modes?
There are at least 3 factors that influence the damping
Internal material damping within the membrane. For a single ply drum head, this is probably small, but if you are using a multi-ply head (e.g. ...
- 2,676
1
vote
Accepted
Sound level emissions (IEC 60704-1) spectrum?
What is the measurement Spectrum?
From BS EN 60704-1:2010+A11:2012 Page 10, Section 4.1 Paragraph 3
The preferred noise emission quantity is the A-weighted sound power
level, LWA, in decibels
...
- 7,771
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