All Questions
Tagged with signal-processing frequency
49
questions
0
votes
1
answer
33
views
Phase-Based Ranging
I've been reading a lot about Phase-Based Ranging (PBR), and it's all starting to become very intuitive.
BUT; There is one technical, but extremely important, detail that seems to escape me. When the ...
0
votes
2
answers
84
views
I don't understand intuitively why the instantaneous frequency is obtained by calculating the time derivative of the phase
I don't understand intuitively why the instantaneous frequency is obtained by calculating the time derivative of the phase
- 11
0
votes
2
answers
85
views
Does sunlight have a modulation frequency?
By frequency, I don't mean electromagnetic frequency, I mean modulation frequency. For example, I can put a PWM square wave on an LED at some frequency, which I can detect with a photodiode and a ...
- 1
1
vote
2
answers
47
views
Is it possible to, like white noise, excite all audio frequencies equally, but with a more immediate & less random burst? Like a signal discontinuity?
I am trying to generate an audio signal that, like white noise, has "equal intensity at different frequencies, giving it a constant power spectral density", but unlike white noise, can be ...
- 321
0
votes
1
answer
66
views
How do you extrapolate frequency data from FDTD simulation time data?
Context: Im a PhD student who plans on doing research in theoretical plasmonics/nanophotonics, so I am studying up on understanding FDTD. I am having a bit of a conceptual issue regarding ...
- 1
1
vote
1
answer
215
views
Why don't podcasts played at faster speeds sound higher-pitched?
Many podcast apps allow you to listen to podcasts faster than the speed at which they were recorded (typically at x1.25, x1.5, x1.75, and x2 speeds).
If these apps are simply replacing the sound's ...
- 48.4k
2
votes
3
answers
522
views
Why does audio signal amplitude always fall off at higher frequencies?
In the frequency spectrum of every real audio sample that I've ever seen, the amplitude of the frequency components is always higher at low frequencies, then rapidly falls off at higher frequencies.
...
- 1,004
3
votes
2
answers
73
views
In what respect does the wave pattern of a noise and music differ?
Does the wave pattern of musical sounds contain only harmonics (other than the fundamental frequency) while noise contains random overtones (that are not harmonics)?
- 1,064
1
vote
0
answers
24
views
Minimum Observable Offset Frequency in Leeson's Formula
It has been argued in some publications that the age of the universe represents a lower limit on observable frequencies (in their paper, corresponding to a value of $10^{-17}$ Hz). The authors do not ...
- 100
1
vote
1
answer
53
views
Wavelength and frequency associated with a wave pulse
What are the definitions of wave length and frequency of a wave pulse?
- 468
0
votes
2
answers
4k
views
How do I convert the Amplitude from Power/Amplitude spectral density?
I've started working on PSD for seismic signals. In theory, PSD signal can be expressed in 2 ways. One in $(PSD=g^2/Hz)$ and other in $PSD=((meter/second^2)^2/Hz)$ and also ASD=(√PSD). Here $g$ is the ...
- 11
19
votes
6
answers
3k
views
Can we quantify the pitch of a sound that is a mixture of many frequencies?
How is the pitch of a sound defined quantitatively when it is a mixture of many frequencies? For example, the sound emitted by a plucked guitar string, or say, the pitch of somebody's (normal) voice. ...
- 11.8k
1
vote
1
answer
64
views
Is this a good use of the convolution?
I would like to replicate the real response of an instrument to some signal. Here's what I have in mind: I generate some ideal signal. I then add Gaussian noise to it to produce a realistic signal s(t)...
- 150
0
votes
0
answers
79
views
Physical interpretation of FFT frequencies
I need to calculate the PSD of a discrete signal and want to compare it to other processes. By Nyquist theorem, I only can account half of the frequencies.
Assume I have a signal of length $N=100$, ...
1
vote
1
answer
88
views
Data transmission through optical fiber and copper wire
I read the following in one reference: A copper wire (twisted pair), the link traditionally associated with low bit rate transmission, is still in use in the modern data centers transmitting data at ...
- 111
0
votes
1
answer
53
views
Is there any known result about the "average period" of a complicated oscillating function?
Say we have some frequency spectrum, $f(\omega)$, where
$$
f(t) = \frac{1}{2\pi} \int_{-\infty}^\infty d\omega \; f(\omega)e^{-i\omega t},
$$
and we know that $f(t)$ is some sort of ...
- 188
9
votes
2
answers
5k
views
What is meant by 2D fourier transform of an image?
I have some questions about this interesting concept I came across about 2D Fourier transform, please...
Firstly, the Fourier transform of a 1D signal (such as a sound recording) is as follows:
The ...
user315366
1
vote
1
answer
43
views
What is the relation between the frequency vector and the Nyquist frequency?
When trying to comprehend the concept of Nyquist frequency in FFT, I came across the following definition for half of the frequency range:
$$f = -f_{n}/2:df:f_{n}/2-1;$$
where $f$ represents the ...
- 753
1
vote
1
answer
166
views
What is the meaning of the absolute of the Fourier transform in this context?
In a course talking about Fourrier transform and Nyquist frequency, there is this sentence that I can't understand:
"If a signal has $|F(w)| \geq 0$ only for frequencies till f, than such ...
- 113
1
vote
1
answer
96
views
Can we decompose sound like white light is decomposed (dispersed) in different colors?
When we send white light through a prism, the light is decomposed in the colors that constitute it due to the different velocities which different frequencies. Is there a way to decompose "white ...
2
votes
2
answers
2k
views
Amplitude based "filtering"
Standard filters in electronic circuits are devices that allow a certain range of frequencies to pass through while attenuate other frequencies. I was wondering if something similar could be built ...
- 484
14
votes
10
answers
8k
views
Why does a capacitor act as a frequency filter?
What is it about a capacitor which allows it to filter frequencies?
I understand the construction of a high-pass RC filter, and the mathematics behind it, but I'm struggling to find an explanation of ...
- 267
1
vote
1
answer
141
views
Intuitive explanation of Nyquist rate?
Is there an intuitive way to understand Nyquist rate (i.e., that, in order to prevent loss, an analog signal must be digitized at a rate twice as high as the highest frequency component of the signal)....
- 111
0
votes
1
answer
132
views
Frequency of signal means changing or moving?
I saw some where frequncy means how fast a signal is changing and i am confused.
Since frequncy means how much cycle a signal completes in unit of time and we may say how fast a signal is moving but ...
- 17
0
votes
0
answers
66
views
In square wave modulation: should the low frequency part of the graph not take place in the low amplitude part of the pulse?
I try to get my sound program right, and hoped to find some help here with the understanding of frequency modulation by a square wave.
My modulation looks like this: (please excuse if my formula ...
- 101
0
votes
1
answer
2k
views
Help in understanding frequency vs phase difference graph
The following graph in my textbook plots the relationship of external driving frequency and phase difference of the driver and a system. From this question (Why dosn't amplitude increase when ...
- 167
0
votes
1
answer
58
views
Catching the beat! [closed]
I'm lately fascinated with the whole "beat" concept, and have been doing some experiments. I'm trying to capture the beat waveform on an oscilloscope in run mode, but am having no luck. I'm putting a ...
- 13
2
votes
0
answers
86
views
The validity of some "applications" of the uncertainty principle
Given a $L^2$ function $f$ with $\int_\mathbb{R}xf(x)dx=0$, define its variance to be $\sigma_f^2=\int_{\mathbb R}x^2f(x)dx$. The uncertainty principle states that $\sigma_f\sigma_\hat f\geq 1/4\pi$,...
- 1,335
5
votes
0
answers
59
views
"Synchronization" Probability of Multiple Waves with Varying Frequencies
Update 1: I've done some digging and I think this is related to signal coherence, namely, that I'm seeing a coherence time of ~3 σ, which is consistent with the definition where Ct=1/Δv where Δv is ...
- 287
1
vote
2
answers
318
views
Why we use Nyquist frequency limits
Can someone in simple terms why you would use Nyquist frequency limits when processing a signal? What benefit does it provide, and how does it affect the results? And how does it relate to the Nyquist ...
- 125