# Tag Info

## Hot answers tagged acoustics

3

The beam width is proportional to the wavelength $\lambda$ divided by the aperture width $L$. Audible sound frequencies are are in the KHz range with wavelengths between approximately 17 m and 17 mm. Whereas visible light wave lengths are in the micrometer range. So sound apertures would have to be vastly larger than light apertures to achieve similar beam ...

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Well, if you want to be mathematically correct (in an objective manner), the noise will be doubled. As niels nielsen mentioned doubling the power will yield a 3 dB increase. Now, whether this results in a doubling of loudness as a perception metric, then the answer is most probably no. According to this book and further references therein, as well as the ...

3

Your ears detect loudness on a logarithmic scale, where doubling the strength of the noise source results in a slight but noticeable increase in the perceived loudness, which is +3dB when measured on a sound level meter. So, if one washing machine generates (for example) a 75dB noise level, adding a second washing machine will measure (75 + 3) or 78dB on a ...

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Your last equation is for differentials, it is only exact when the differences ($dT,dv$) are infinitesimally small. For any differences that are finite the answer will be close but slightly off. What you did is essentially a Taylor expansion. If you write $T$ as function of $v$ (assuming $\mu$ is constant) you can use a value at known $v=v_0$ to get an ...

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Here are some things for you to think about. First, to reduce the resonant frequency of a metal tuning fork requires the removal of enough metal from the crotch of the fork so as to significantly increase the effective length of the tines. It is highly doubtful that you did that with just a couple of passes of a metal file. Second, to get a reliable ...

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The shape effect on fundamental pitch is slight, but the effect on the overtone series is significant. Most wind instruments have cylindrical shapes for this reason, and also because square cross-section pipes with bends in them are more difficult to fabricate. This is a topic about which a lot has been written in the field of musical instrument acoustics/...

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I believe the question can be rephrased (more clearly) as follows: "when we collide two glass balls (or two steel balls), we hear multiple collisions. The intervals between collisions change from long to short. Why?" Take a look of this video https://www.youtube.com/watch?v=k1id4a4EU4M (Pay attention to time 1:01) when he casually collided the balls you ...

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Force gets generated by the interaction of the current flow through the coil and the magnetic flux of the motor. Hence you design to have current and flux to be perpendicular to each other and the motor is designed to concentrate all the magnetic flux in the gap. The current in the coil does indeed create a magnetic field as well, but that is an undesirable ...

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The speed of sound is found (both mathematically and experimentally) to be: $$v = \sqrt{\frac{P}{\mu}}$$ . Let's understand this formula a little, it depends on pressure directly (although to $1/2$ power) means if we increase the pressure the speed will be increased because more pressure means that molecules are hitting the walls of container strongly and ...

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Like very well the rest of the contributors commented "wave-beams" (apologies for the slight abuse of the term) are not uncommon at all. Medical imaging is just one field where they are used. Sonars is another possible application (both transmission, and reception). In general, in acoustics (whether it is ultrasound, underwater, or "conventional acoustics") ...

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Wave beams require to have a transversal section of lenght of the same the order of magnitude than the wavelength. Whereas for light, we can get very tiny and focused beams (of $\mu m$ order), for sound the wavenlength (of centimeter or meter order), you cannot get beams s focused. Hence the utility of such beams to either transmit information, or focus ...

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A vibrating object like a wine glass or a bell is a very complicated system. It is possible for a wine glass, for example, to exhibit multiple resonance modes in which the modes are weakly coupled i.e., energy in one mode is slowly shared with other modes. This means the quality of the perceived sound will shift perceptibly on a timescale of ~seconds. Note ...

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Hold it against a surface (sounding board). Or put it on a quarter-wave resonator box. Or hold it against your teeth or on your skull behind the ear.

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Your method is completely fine and it is the one that should be used. Let me write it down once more $$v = \sqrt\frac{{T}}{{\mu}}$$ $$300 = \sqrt\frac{500}{\mu}$$ $$\mu = \frac{500}{90000}$$ $$\mu = \frac{5}{900}$$ No we want $v=312$ so let's just put it in the equation which you have stated $$312 = \sqrt\frac{900T}{5}$$ $$\frac{312\times 312\times 5}{... 1 This sounds like destructive interference interacting with your attempt at driving a resonance. Normally when whistling or singing in the shower or a stairwell, certain pitches get nicely amplified by resonance. These room modes are standing waves where the pitch fits into an integer number of wavelengths between reflecting walls. The sound source ... 1 I believe that Erlend gave a quite instructive answer, so I will try to stand only on one point of your question. You kinda mix loudness, amplitude and frequency in a more objective way than a subjective one (as would the inclusion of loudness in the conversation would demand), and you seem to be interested to know if the frequency of a wave would affect (... 1 Assuming that you are driving straight into the building, the observer in the building hears the sound coming from your moving car with frequency shifted due to the Doppler effect. The frequency is given by:$$ f_2=\frac{c_s}{c_s-v} f_1 Here, $c_s$ is the speed of sound in air and $v$ is the speed of your car. You can find the derivation of the frequency ...

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Well, Qqwy, has provided a nice answer to you, so I am just gonna try to add up to that. As has already been mentioned, the actual realization of an active noise cancellation device has many implications. Latency being just one of them (more of them include imperfections in modelling, transfer function of the components, incorrect equalization and a whole ...

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It is a very fundamental good question and it is not limited by acoustical waves but is also valid for all harmonic wave propagations bounded by a reflecting surface. Here it is the room, ie, standing waves are observed also for electromagnetic waves very similarly. I find it helpful to clarify some points first, especially for other readers following this ...

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