8 votes

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 ...
  • 141
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 ...
3 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, ...
3 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-...
  • 21.6k
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 - ...
  • 9,414
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 ...
  • 2,135
3 votes

Determining frequency of an ultrasonic transducer

If you're talking about a "bare" transducer (i.e., not a module with its own driver), you can just hook it up to an oscilloscope, hit it with a narrow pulse of voltage, and look for the decaying ...
  • 6,814
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 ...
  • 5,272
2 votes
Accepted

Piezoelectric matching/backing layer materials

I am assuming that you are using the TDC1000 Analog Front End (AFE). This is because you are using an image snippet from the the image below. If so I suggest that you use cyanoacrylate (CYA) glue ...
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

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 ...
2 votes

Microspeaker enclosure design for headphones

the equations scale linearly for the linear dimensions of enclosures. However, here is why micro-enclosures don't get designed according to the same laws and equations used for full-sized speaker ...
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 ...
  • 21.6k
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 ...
  • 2,347
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 ...
  • 21.6k
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 ...
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 ...
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 ...
  • 21.6k
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 ...
  • 2,586
1 vote

Does the stress on exhaust hanger amplify sound transmission into the vehicle chassis?

Consider a metal rod. You put your ear to one end. Someone "pings" the other. You will hear the ping thru the metal. Now add a wad of cotton balls at your end and repeat. Press your ear firmly on the ...
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 ...
1 vote

Grate that does not cause air rush noise?

If it is a metal grate, the sound may be amplified by the grate itself vibrating, and possibly transferring the vibrations into the duct and then the structure of the building. A plastic grate (if ...
  • 12.6k
1 vote
Accepted

What is tonal masking?

Tonal masking is using tones at specific frequencies for sound masking, as compared with using noise containing a continuous band of frequencies. In most practical situations noise is more effective ...
  • 12.6k
1 vote

How can I calculate headphone driver excursion?

I doubt that the calculator you referenced is relevant for headphones. A fundamental difference between headphones and loudspeakers is that headphones transmit energy to the small, (almost) sealed, ...
  • 12.6k
1 vote
Accepted

How do I convert coefficient values from 1/3 octave band to 1/1 octave band?

If I'm understanding your question correctly, you want to sum up levels given as 1/3 octave bands into 1/1 octave band resolution. This can be accomplished by decibel summation: $L_\Sigma = 10 * log(...
  • 106
1 vote

Sudden increase in noise levels - subway noise -happend overnight

It is possible that because of percolation, the moisture content of the layer of dirt between you and subway has changed to near optimal compaction, which is in the range of 12 to 24 % in siltyclay, ...
  • 21.6k

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