Questions tagged [signal-processing]
The subfield of electrical engineering that focusses on analysing, modifying, and synthesizing signals such as sound, images, and scientific measurements.
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Two-Ray Ground-Reflection Model: Understanding the Difference in Phase Offsets at the Receiver
Currently, I'm trying to understand the Two-Ray Ground-Reflection Model.
During my research, I came across the following simplification expressing the received power as follows (taken from Wikipedia):
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Is the strongest acoustic signal always the closest?
I have a single beam echosounder that I use to measure the distance to an object underwater. It emits an acoustic pulse and listens to the reflections. Using the time of flight and the strongest ...
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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 ...
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How do computers store sound waves just by sampling the amplitude of a wave and not the frequency?
All of this just doesn’t make sense though.
I mean, doesn’t the amplitude represent the loudness and the frequency the pitch? Aren’t they completely independent from each other?
Is the book just ...
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Avoiding radar detection using active noise control instead of a stealth fuselage
was reading about different stealth technologies used by modern aircrafts to avoid radar detection.
Wouldn't it be easier to have a receiver on the airplane listening on the radar frequencies and then ...
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Doubt on time invariant system
Now I am delaying the output of a system (which takes $x \left( t \right)$ as input and gives $t \cdot x \left( t \right)$ as output) by $T$ then final output is:
Let's denote the output of the ...
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Modeling an Acoustic Reflection from a Wall
I am trying to simulate the reflection of a sound ray, that goes from a sound source, bounces off a wall, and is received by a microphone.
The wall has a an absorption coefficient, and a specular ...
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Energy spectral density vs power spectral density vs power spectral density per unit time
I recently started research to measure the voltage noise spectrum of materials to study their phase transitions. Before understanding physics, I am now confused by the three terms used in literature:
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Determining the location of light receivers using signals propagating in anisotropic media
Problem.
I have a set of $16$ light receivers with entirely unknown locations, and a pair of light transmitters with exactly known locations. One light transmitter is stationary, and located near to ...
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What is the physical meaning of the pressure of an acoustic point source being complex?
Context
From various sources of Acoustics (such as "Acoustics -
An Introduction to Its Physical Principles and Applications" by Allan D. Pierce and "Fundamentals of General Linear ...
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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 ...
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Why does superposing an infinite number of waves of different wavenumbers eliminate periodicity and may sometimes result in a localised wave?
I am studying how wave packets are defined in quantum mechanics, but I am finding it hard to intuitively understand why superposing an infinite number of waves of different wavenumbers $k$ may ...
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The solar spectrum on the time domain
This is the solar spectrum by wavelength:
By formula $c=f\lambda$, we can plot the solar spectrum over the frequency domain:
Then we can conduct inverse Fourier transform to transform the plot into ...
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Can multi-instrumental sound be reconstructed from a waveform?
This question came about when I saw someone wearing clothing with a waveform on it. I wondered if it would be possible to reconstruct the original sound from the printed waveform.
I understand that a ...
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Why do the signals for second harmonic generation and third harmonic generation differ in the strong focusing limit (strongly focused gaussian beam)?
In Ward & New (1969), the expression for second harmonic generation (SHG) and third harmonic generation (THG) intensity is derived for the focal volume of a strongly focused gaussian beam (axially ...
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Recovering Decay Constant from Fourier Transformed Exponential Decay in NMR
I'm currently in a NMR lab for an undergraduate physics class, and I am attempting to determine the decay constant $\tau$ (e.g. $T_2$) associated with a free induction decay signal. However, our ...
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It is possible to express the convolution between two quantum functions $\psi_{1}(x)$ and $\psi_{2}(x)$ in terms of a inner product?
The question of the title is due to the following methodology. Let us consider two arbitray quantum functions $\psi_{1}(x)$ and $\psi_{2}(x)$, such that the convolution between them is
$$\left\lbrace \...
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Spectral representation of a white stationary process
I am trying to better understand the spectral representation of stochastic processes. From the book "Spectral Analysis for physical applications" by Walden and Persival:
The spectral ...
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Why does audio signal amplitude always fall off at higher frequencies?
In the frequency spectrum of every real audio sample that I've ever seen, the amplitude of the frequency components is always higher at low frequencies, then rapidly falls off at higher frequencies.
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What do I hear when listening to a computer-generated sine wave?
When I use a sine-wave generator (such as this one), I give credit to the software and my hardware that a pure sine wave is produced (as close as is technologically possible) — that is, no harmonics. ...
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How to convert from a wave-reading?
I have a series of wave-readings which show wave amplitudes pr. time unit for different events. So on the $x $-axis we have seconds, and on the $y$-axis, wave height.
If I want to convert this to a ...
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What's the formula of SNR (Signal to Noise Ratio) to dipole antenna array (eg, LOFAR) look like?
It was wellknown that the SNR of single dish telescope reads
$$s/n=\frac{P_s}{P_n}=\frac{P_{s}}{T_n}\sqrt{\frac{t}{B}},$$
where $P_s$ is the collected power, $T_n$ the noise temperature, $t$ the ...
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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)?
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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 ...
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Fourier vs. Laplace transforms
Electronics books often use Laplace to analyze circuits, while in physics we use Fourier, most of the times... if not always: from complex impedances to electromagnetism, quantum mechanics, Green ...
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Signal Processing – Discrete Fourier Transform and Incomplete Fourier Series
I'm working on a paper where I'm collecting sound pressure data from a chord's wave and trying to create a frequency spectrum to find the individual frequencies that make up the chord.
However, I can'...
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What's the smallest signal to noise ratio for which a signal has been extracted?
Suppose we have some physical variable $y$ that is changing in some way and we want to detect this change in the presence of noise (e.g. white noise) in that same physical quantity. For example $y$ is ...
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How to "classify" signals?
I have some signals and I want to classify them into different types. Signals are all sine shape signals, some might have glitches. I know I could classify them base on frequency or amplitude, but is ...
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Accidental coincidence formula
Suppose you have a setup with $n$ scintillators coupled with $n$ PMTs. These signals are passed to a discriminator. I am observing some signal, let's say this signal is coming from cosmic rays and I ...
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Can you make a faraday cage intended to effect electrical wires?
Generally with a faraday cage your object is completely surrounded and encapsulated within the cage. Let's say I have a wire with electronic signals flowing through it, say an ethernet cable that is ...
