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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 high, it would be fairly effective. But I don't think your building regulations will let you build a 140 foot high wall, even if you can afford to do it! The bass ...


4

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 reduction is simple to obtain and a 20 dB reduction is nearly impossible to obtain. Even completely burying a highway does not eliminate the noise. While not a ...


3

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, as in most heatpump units. A 3-blade fan running at 1750 RPM will produce a hum at 88Hz. This will have a wavelength of about 11 feet and will diffract strongly ...


3

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-hertz has a wave length (Lambda) of 340/500 = 68cm, but at 170-hertz lambda = 200cm. And much of the noise generated by the heat pumps will go around or be ...


3

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, (otherwise you would not be able to hear any wind instrument playing a note!) and the sound wave outside the pipe is a traveling wave. Note, the "end correction" ...


3

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 coefficient is dependent on frequency meaning that it will absorb some frequencies better than others. It's also dependent on the angle of incidence. Google will bring up ...


3

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 were co-located with the speakers themselves). Delays on order of a tenth to a half a millisecond were needed and the amount of delay had to be adjustable to ...


2

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 eardrums, these little guys don't require soft surrounds to accomodate large cone excursions. the flexure of the material itself is adequate for use as a surround....


2

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 waveform of its self-resonance. Measure the frequency of that waveform.


2

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 also known as crazy glue. It is important that the transducer has good mechanical coupling to the stainless steel material. I have tried a material similar to ...


2

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 boxes: the primary objective of full-sized speaker enclosure design is to manage the resonances of the box/driver system so as to prevent large response peaks in ...


2

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 - inductors and motor windings. The current through them will cause attraction or repulsion between the turns of the coil and cause them to flex a little. The iron ...


2

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 reverberation, will help the attenuating of noise. These decorative objects have to meet fire and safety codes and be easy to wash and maintain. And they ...


2

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 several times bigger than the wavelength of the sound, and at low frequencies that means tens of meters. It is impractical to make the actual sound producing ...


2

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 same order are transparent. A lot of bass noise travels through foundation. Sound absorbing panels may be more effective.


2

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 insulate your house, using cork. Cork panels work very well for sound insulation. Especially if you manage to get egg crate shape, though it can be expensive depending ...


1

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 stiffness, and can only carry load through in-plane tension. You can definitely have traveling waves in membranes. E.g. a drum head is a membrane. See https:...


1

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. the batter head on a typical snare drum), it will be larger and could get pretty complicated to model Friction at the interface of the drum head to the drum. ...


1

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 It is not correct to assume that a peak at 10kHz is outside the measurement range - you can reduce your 75dB measurement by -2.5dB according to the curve shown ...


1

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 such a thing is available) may be quieter because the material has more internal damping than metal.


1

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 cotton. The sound will be muffled if it comes thru at all. When your vibrating exhaust is attached directly to the car, the car picks up and can amplify the ...


1

As @SolarMike pointed out the acoustic waves might harm the fish because the sonic speed in water is approximate $1484 \frac{\text{m}}{\text{s}}$ (at $20° \text{ C}$), this is quite high compared to the sonic speed in air which is approximate $330 \frac{\text{m}}{\text{s}}$. This might lead to the disorientation of the fish population close to your boat. The ...


1

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, volume of air trapped between the headphone and the structure of your ear. That is completely different from a loudspeaker which is designed to transmit energy ...


1

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: $L_\Sigma = 10 * log(10^\frac{L1}{10} + 10^\frac{L2}{10} + 10^\frac{L3}{10})$ Where $L$ are levels in dB. Please see here for an online summation tool.


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Yes you can do this in fact, there are acoustic devices used by the military to detect the location of snipers. However, this is something of a special case and it relies on detecting not just one sound but a well understood acoustic signature. In the case of a bullet you have the sound of it being fired and the sound of the sonic boom as it passes. In fact ...


1

You may be thinking of a device with multiple microphones some distance apart (enough that you can measure the delay between each one), which you could then use to triangulate the direction and distance of the sound source. Such a system was used to track submarines during the second world war. RAF Nimrod planes would drop buoys into the ocean which had ...


1

I'm not sure you understand what "acoustic impedance" is. The string by itself has a resonant frequency defined by its elastic modulus, the applied longitudinal tension, and length. If you really want to know how well it couples to the air around it, I suspect you'll be diving into an ugly bit of math. For one thing, unlike a speaker cone or a trumpet (...


1

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, assuming your strata is CL, ML, SC. These are sensitive to moisture ratio and at optimal compaction transmit sound better. Some change in moisture is seasonal, ...


1

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 as metal chain links to hold it up. If you use rubber, you may dampen the sound, and if you mount right to the wood, that's when divots may form on the gong. ...


1

Currently, honeycomb cores are sometimes faced with an adhesive film between the Prepreg skin and the core. But you seem to be describing a viscoelastic midlayer. This arrangement could be simulated parametrically with FEA and the polymer’s FEA Support Test Data. (Parametric FEA model: adjusting thickness and surrounding core/facesheet assembly material ...


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