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## Multiple PDM mic recording

How to record multiple PDM mics at 16KHz? What is a recommended soundcard/HW that can be used?

How to record multiple PDM mics at 16KHz? What is a recommended soundcard/HW that can be used?

## Threshold of hearing compensation

inThere are several new consumer headphone products on the market that allow you to measure your threshold of hearing using an app on your phone and...

There are several new consumer headphone products on the market that allow you to measure your threshold of hearing using an app on your phone and then auto-adjust an equalizer to boost the areas where your threshold is high (indicating hearing loss at those frequencies). Iâm no audiologist but this seems suspicious to me; I donât think having a high threshold is the

## Homodyne complex frequency shift

inHi, the input signal is sin(t), I multiply it with cos(t) to get the I component and sin(t) to get the Q component. So...

Hi, the input signal is sin(t), I multiply it with cos(t) to get the I component and sin(t) to get the Q component. So then I(t)=sin(t)*cos(t)=0.5*sin(2t) Q(t)=sin(t)^2 I would expect only the DC component to persist, but instead I have two quickly wiggling waves. What is missing to shift 1kHz to DC without introducing the mirror frequencies? Thanks in advance!

## magical Black Hole image

inThe Event Horizon Telescope team of course deserves a huge amount of credit for their results. But it's interesting how they got there. ...

The Event Horizon Telescope team of course deserves a huge amount of credit for their results. But it's interesting how they got there. Here's an article with some non-technical discussion: https://fivethirtyeight.com/features/forget-the-black-hole-picture-check-out-the-sweet-technolog y-that-made-it-possible/ Their data is too noisy to actually create a black hole image. So they a

## short pulse generation with DSK6416

inHello, I'm trying to generate short pulses with DSP's 32-bit timer. I'm using the DSK6416 board (@1GHz) . I need to have pulse widths as...

Hello, I'm trying to generate short pulses with DSP's 32-bit timer. I'm using the DSK6416 board (@1GHz) . I need to have pulse widths as short as 10ns-50ns and be able to change the duty-cycle. I try to read the CNT register of the timer and set DATOUT to be driven on TOUT pin of timer when the proper width has reached. The problem is that when I use the TIMER_setDatOut API it is not possible...

## 5-point stencil or Savitsky-Golay for differences

inI had some code computing the second difference of a sampled signal as (x(n-1)-2x(n)+x(n+1))/(square of interval) I only needed a crude estimate...

I had some code computing the second difference of a sampled signal as (x(n-1)-2x(n)+x(n+1))/(square of interval) I only needed a crude estimate of the second derivative in this case. Then I came across "five point stencils" By this method, the second difference is (-x(n-2)+16x(n-1)-30n(n)+16x(n+1)-x(n+2))/12/(square of interval) And then 5-sample Savitsky-Golay formula, which seems rath...

## Efficiency of Midi->Freq and back

inI'm writing something with a lot of conversions between midi and frequency in a timing tight situation and I'm wondering about efficiency. (in C)...

I'm writing something with a lot of conversions between midi and frequency in a timing tight situation and I'm wondering about efficiency. (in C) What are the community's experiences with this? Would a 1 or 10 cent interpolated lookup table be more efficient? Is there a way to make the log less expensive? Does caching and comparing the last input and output help? Thanks for any insig...

## High-order EMA works great - but why?

inI have a classic digital PLL with multiplier-based phase detector, intended to lock at 50Hz. The sampling frequency Fs is 25kHz, the...

I have a classic digital PLL with multiplier-based phase detector, intended to lock at 50Hz. The sampling frequency Fs is 25kHz, the loop filter bandwidth varies between Fc=10Hz to 40Hz, as I am experimenting with different filter structures. The PLL itself works like a charm and my reference filter is a 500th order FIR: fir1(500,Fc/(Fs/2)). To a reasonable degree the loop converges to a ...

## FFT interpolation Matlab

inHi, I am trying to use interpolation to detect an FFT peak between bins however my interpolation results in the same peak as the FFT. I am...

Hi, I am trying to use interpolation to detect an FFT peak between bins however my interpolation results in the same peak as the FFT. I am inputting a 50Hz sine wave.. Sampling freq is 6500hz and I have 2048 sample points. There fore my bin freq is 3.17hz which multipled out gives me a 50.8hz nearest bin frequency which is what my code is giving me. I am trying to see where my i

## Ultrasound beamforming

inHi, A typical beamforming method widely used in ultrasound technology is to apply delays between channels and then summing the signals of all the...

Hi, A typical beamforming method widely used in ultrasound technology is to apply delays between channels and then summing the signals of all the channels. However, when properly calculated delays are applied, it could happen that the phase of the arriving signal is 180 deegres (half the ultrasound wavelength) shifted between channels and summed amplitude is decreased. This results

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