# Tag Info

9

In a more general sense, the electrical concepts of inductance, capacitance and resistance are equivalent to mass, spring constant and friction in the mechanical world. Voltage becomes force and current becomes velocity. For example, the suspension in a vehicle is a carefully-tuned low-pass filter that uses the mass of the frame and body, the springs on the ...

8

Yes, for sound specifically there is a term called "acoustic impedance" that, just like electrical impedance, is frequency dependent. Acoustic impedance results from the acoustic wave equation, which takes the same form as the electromagnetic wave equation. So any solid has an acoustic impedance just like every conductor has an electric impedance. Acoustic ...

8

Some reasons why noise reduction in vehicle cabins is not a standard feature, yet: As @Trevor Archibald states, safety is a very good reason. There is still a need to hear some noises from outside the vehicle such as the sirens of emergency vehicles: police, ambulance, fire fighters truck Hearing car horns from other drivers is still needed The sound of the ...

5

Unless they have hearing loss, young people tend to be able to hear a larger range of sound frequencies than older people, particularly higher frequencies: Some security companies recently began manufacturing machines designed to emit an annoying sound that prevents teenagers from loitering outside stores and shops. Teens are effectively driven away, but ...

5

There are analogs to filters in lots of mechanical systems. In fluid systems prone to pressure spikes perhaps because they use a fixed displacement pump, an accumulator will be used to filter out those spikes to prevent damaging other parts of the system. A vibration isolator acts in much the same way. Sometimes they're used as is. Other times, for more ...

4

This is a very interesting question. I would say, yes and no. The headphone jack is not designed for this at all, and you won't get much power out of it. My preliminary research indicates that an iPhone 4 headphone jack may support up to 60 mW of power output. This, however would be AC power, like sound. So, I think you could put a full bridge rectifier in ...

3

Your understanding of the issues is good. Q1: It's not overkill at all. All of the elements you've mentioned are needed. Q2: The low-pass filter frequency needs to significantly attenuate all frequencies above 1/2 the sampling frequency. It makes sense for a 'low fi' arrangement to reduce the filter frequency a bit so as to simplify filter design which ...

3

First, can you really actuate white noise? If yes, White noise would probably show many natural frequencies and harmonics. However, make sure the actuation bandwidth is sufficient for your frequency range. If the piezo can be adjusted to your frequencies of interest, a more deterministic approach would be to do a frequency sweep. For that, start from the ...

3

The reason for the humming noise is improper grounding. Audio signals are low voltage level AC signals (over simplified). An audio signal could be for example 1V, 1 KHz signal. When there is improper grounding, a low level noise signal example 10mV 50Hz can get coupled to the audio signal causing humming. (Values are made up) I would suggest installing ...

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 ...

3

How do you define a microphone? Because there many ways to detect mechanical vibrations, but all of them could fit in a more or less relaxed definition of microphone. For example, you could measure temperature variations on a noise-absorbing foam. Or vibrations on a building wall for low frequencies, etc. Following your concern of surveillance: For ...

2

The first big problem is with your speaker placement; the 'anti-noise' speaker should be as close to the 'noise' speaker as possible. Another big problem is with the speakers you are using; they are way to small for an open-volume system. Even with both of these issues fixed, I doubt you will be able to get significant noise cancellation. The simple ...

2

I don't think there's enough room in a comment to add all of this, so that's why I'm posting this as an answer. What do you mean when you say, "I have implemented LMS on Labview"? What is LMS? What FPGA board are you using? Is this an off-the-shelf part or some home brew hardware? You're not happy with your test results - what are they? Can you post before ...

2

You could make a water drain trap. Drill a vertical hole that meets the microphone hole somewhere along its length, with a drain hole sloping down for the water to escape. You could then make a step change in diameter in the mike hole (for example between the pink and blue parts in our drawing) to stop the water getting past the drain. Since you appear to ...

2

Because the file is compressed. The sample rate and bits per sample are parameters of playback after decompression. The file size is for the compressed format, the amount of data that needs to be downloaded, not the amount of data that reaches the digital-to-analog converter.

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

That long audio cable is acting like an aerial. Does it run close to any mains wires - in the wall perhaps? You will be better off getting a quality shielded audio cable as a first step. If that does not work then you have to consider some filtering.

2

I will first assume you do not have any of the wires crossed here. It is unlikely that the cause is in the CAT6 cable, but here's how to test this: send the alexa signal (red) thru the cable to the mixer. Then, instead of plugging them into the mixer, unplug the OUTPUT (blue) lines from the mixer and connect them to the alexa (red) wires. Then plug the ...

2

what you are calculating is the uncompressed bitrate. However, MP3 uses lossy compression, typically achieving final sizes of about 10% compared to the uncompressed file (for constant bitrates). Therefore you can have the same sample rate, number of channels and bit depths and different MP3 bitrates. See an example matrix from the following website Things ...

1

As mentioned the cable is acting like an aerial. A ferrite core to wrap the cable around a couple of times might help. The comm to the charger comm is grounding it with less resistance as the other answer said.

1

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 are at or near the same location) would result in about 50.5 dB.

1

The standard rule of thumb for adding decibels is that doubling the sound power increases the dB reading by +3dB. Using an on-lone calculator for adding dB's, we find that adding two sound sources that differ in strength by 10dB yields a dB total of 40.25dB. To the human ear, a difference of 0.25dB is completely inaudible.

1

There are Bluetooth adapters available which will hook into audio system via 3mm jack or optical jack and broadcast the music to your headset. However if you want to receive the music into your phone, you need another adapter to hook into your phone audio jack. I have both and they cost me $20 each. 1 Okay, I will go ahead and answer my own question. Since I'll have to deal with an analog signal anyways, coming from the audio output of a mobile device. I'll need an ADC [analog to digital converter] then I'll match that up with a DAC [digital to analog converter] and send that out a TRS plug. This thing will need it's own power supply for it all but I ... 1 Why have the hole perpendicular to the front surface? Angle the hole so that it is slightly uphill when the screen is at the angle as shown. Or, could you fit a membrane on the surface of the microphone and mount it closer to the front face with a larger hole for the entry rhs but smaller hole on the face lhs. 1 Magnetic force microscopy should have sufficient resolution. The principle of operation here is that an external force causes a very small (few micrometers) magnetic probe to vibrate, and then the magnetic field from the sample (e.g. the tape) will cause tiny changes to the amplitude or phase of the vibration. Certainly not practical for a cassette player, ... 1 No. The magnetic flux density available on a tape is way to small to move a magnet with any significant mass enough to produce audible sound. 1 The "X patterns" look like anti-aliasing. If you project the first downward-sloping line of the X back upwards, it will probably intersect one of the "harmonics" lines at the Nyquist frequency corresponding to your sampling rate. For example If you are sampling at 48k samples/sec, your FFT will show a signal at$(24+x)$kHz as if its frequency was$(24-x)$... 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 ...

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