All Questions
19
questions
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
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
65
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 $N=100$, ...
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
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
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
0
votes
2
answers
139
views
Multiple frequencies [closed]
could someone please inform me how it is possible to send multiple frequencies down one wire? I’m referring specifically to a communication protocol known as HART. It seems they send a 4-20mA signal ...
- 29
1
vote
0
answers
63
views
Fourier Coefficients
Suppose i've a two voice samples v1 and v2. Comparatively voice v1 is louder than the v2. If both the voice is spoken by the same person.(Spoken normally as he speaks)
Is it good to state the ...
- 121
2
votes
3
answers
207
views
Use of negative frequency for the sake of simplifying mathematics?
How can we use the idea of negative frequency for the sake of simplifying mathematics if negative frequency does not exist (to my knowledge) in nature ? For example, when plotting the spectra of a ...
- 21