Questions tagged [signal-detection]

The tag has no usage guidance.

Filter by
Sorted by
Tagged with
36
votes
6answers
58k views

The difference between convolution and cross-correlation from a signal-analysis point of view

I am trying to understand the difference between convolution to cross-correlation. I have read an understood This answer. I also understand the picture below. But, in terms of signal processing, (a ...
15
votes
2answers
12k views

Add odd/even harmonics to signal?

How do I add odd or even harmonics to a floating point signal? Do I have to use tanh or sin? What I'm trying to do is achieve some very simple distortion effects, but I'm having a hard time finding ...
15
votes
4answers
16k views

Scipy - Audio Processing

I am looking for good tools for Audio signal processing. e.g Speech & music analysis, automatic language identification, etc. Does the Scipy library provide functions for audio processing? Does ...
14
votes
5answers
2k views

Identify Where Singing Starts in a Voice Only Recording

I have a little karaoke-style app where a user sings 4 lines of a song, with a one second gap between each line. There is no backing music, so it's voice only, hopefully making the problem easier to ...
14
votes
2answers
4k views

Relationship between entropy and SNR

In general any form of enropy is defined as uncertainty or randomness. In a noisy environment, with increase in noise, I believe that entropy increases since we are more uncertain about the ...
12
votes
2answers
3k views

What statistic is used to determine presence of a signal in noise?

This is a detector problem I believe: I am being stumped by what appears to be a simple problem. Basically, I have a band of interest. If signal energies exist within this band of interest, then I ...
9
votes
2answers
9k views

Noise reduction from very noisy audio

I am trying to write an algorithm that would automatically segment a piece of audio with bird calls recordings. My input data are 1 minute-long wave files and on the output I would like to get ...
9
votes
1answer
990 views

Ultrasonic signal detection

I have created a fairly simple TDOA system that uses ultrasonic signals emitted from two speakers to geolocate (relative to the speakers) mobile phones. The two signals are separated by frequency. ...
8
votes
5answers
663 views

Estimators for improved spectral subtraction of noise

Real zero-mean Gaussian white noise, independent of a clean signal $x$ and of known variance is added to $x$ producing a noisy signal $y.$ Discrete Fourier transform (DFT) $Y$ of the noisy signal is ...
8
votes
2answers
2k views

Fast pitch recognition

I need to detect pitch (measure signal frequency) while the musicians play music, giving a warning if they are out of tune, but music happens to be a bit too fast for FFT (Fast Fourier Transform). ...
8
votes
3answers
1k views

Determining optimal binary decision rule threshold from observations with unknown priors?

Given only observations of a binary signal perturbed by Gaussian noise with unknown prior information, how can I estimate the optimal decision threshold? ( No, this is not a homework question) ...
8
votes
2answers
1k views

How to define SNR for multiple signals in noise?

I have to estimate the number of signals present in a measurement contaminated by additive noise given $n$-dimensional snapshot vectors $\bf x$, modeled as $ \bf x = \bf A \bf s + \bf z $ where $\bf s$...
7
votes
2answers
917 views

determine two signals with a scale factor

Suppose I have 2 signals from function $f_1(x)$ and $f_2(x)$, respectively, and assume the sampling rate is above Nyquist frequency, so we can restore the underlying functions $f_1(x)$ and $f_2(x)$. ...
7
votes
1answer
2k views

Efficient frequency offset estimation of known signals

Let's say that my receiver will be receiving known data signals that range from the very simple (tone) to the complex (known data sequence that is modulated (PSK/QAM/OFDM/etc.)). What are the most ...
7
votes
5answers
5k views

What are some methods for detecting a sinusoid in noise?

I'm looking for a broad classification on the kinds of techniques available. Something I can use to begin a literature survey. Some details: should be feasible for real-time implementation. Binary ...
7
votes
1answer
601 views

What is averaging and how can it be done?

I'm studying about the analysis of (mainly) fMRI and EEG data. Multiple times it's mentioned that to reduce noise, you can use averaging, but nothing more detailed than that. There never is literally ...
7
votes
2answers
3k views

Detecting a Signal Inside a Time Series Using MATLAB's $ \tt xcorr() $

I would like to find the exact replica of signal A in time series B. I am working with the simple toy example below, in which A is located starting at the 4th position in B. I thought that using <...
7
votes
3answers
2k views

How to classify accelerometer data?

I am trying to detect if a car did accelerate or did brake by using the accelerometer of the iPhone. In the figure below I plotted the collected data. (To collect the data the phone was laying flat ...
7
votes
1answer
226 views

How to Tell How Likely a Signal Is Present in Another One (Variance Unknown)?

I know this is probably a simple question, but I haven't been able to find a satisfactory answer anywhere... Say you have a time series signal of finite length N. Call it $y[n]$. It looks like a ...
7
votes
1answer
2k views

Match Filter in Time-Frequency domain instead of just Time domain. Redundant, or better?

Assume you have a signal, and within it, some pulses are present. A pulse is a simple tone. You know the pulses' duration and shape. (Let us assume that a pulse is made of a couple of cycles, and then ...
6
votes
2answers
1k views

Recovering signal for psk

I am currently working on a product(cant disclose too much details of the actual project) in which some data is being sent via audible(but on the higher freq) sound that is encoded with dqpsk. ...
5
votes
3answers
16k views

Choosing the length of a signal when calculating the FFT

I'm trying to transforming an already know signal from time domain to frequency domain using fft function in MATLAB. And I got different values of amplitude when I ...
5
votes
4answers
160 views

How to measure a detector's performance under extremely complex real-world environment?

I am trying to formalize my understanding of how best to measure the performance of a binary detector. (See previous question here). I had looked into ROC curves for doing this however based on ...
5
votes
1answer
9k views

I and Q Channels

My understanding of I and Q channels is as follows (please correct me if I am wrong): I = In-phase, or real component Q = ...
5
votes
3answers
3k views

Algorithm for detecting the time where the signal is above a threshold

I need to detect the time window where a 1D-signal is above a certain threshold. If it dips below the threshold briefly I'd like to merge the two windows, if it dips below for a longer time, split ...
5
votes
3answers
6k views

Good way to detect pulse with known width with background noise?

I'm dealing with a light sensor tracking a bursting LED. Unfortunately signal is weak and there are other light sources in environment. I've used optical filters on sensor but there is still some ...
5
votes
2answers
133 views

This is about signal processing in the first radar

I read in a book that the first radar was a CW one that was used to detect ships. Since it was CW, did it use Doppler to detect the moving ships? What was the signal processing used in it? Is there ...
5
votes
2answers
1k views

Create Matched Filter Reference Signal when Scaling Unknown

I am working on a problem which raised what should be a simple question, but I'm stuck on it. The objective is to detect a shifted and scaled version of a known signal in the presence of Additive ...
5
votes
2answers
2k views

Is there a way to reduce the covariance matrix of several source signals to the dominant source signal?

The problem I have can be seen in the context of DoA estimation or blind source signal separation and similar fields, where several source signals are observed by several antennas (or by an antenna ...
5
votes
2answers
470 views

Are Amazon Echo ads embedding an ultrasonic signal to suppress recognition of the Alexa keyword?

Related to High audio frequencies in television broadcast My cell phone samples at 48000 samples/sec so the FFT app I installed can only detect frequencies up to 24 kHz. If anyone has an audio ...
5
votes
1answer
306 views

Received Morse Code signal-to-noise ratio?

I have some digital recordings of some received over-the-air CW broadcasts of known plain-text (W1AW code practice) at known WPM code speeds, but in moderate to heavy RF noise and fading. Can I ...
5
votes
2answers
919 views

How to calculate the phase shift AND time delay of non-periodic signals

Say I have two non-periodic signals, $f_1(t)$ and $f_2(t)$, with Fourier transforms $F_1(\omega)$ and $F_2(\omega)$. Basically, I need to line up $f_1(t)$ and $f_2(t)$ as close as possible, and I am ...
4
votes
4answers
13k views

Simple and efficient algorithm to detect frequency and phase of a sine signal

I need an algorithm to detect frequency and phase of a pure sine signal. The frequency of the input signal changes between 0 and 100 Hz. The value of the signal gets captured with a frequency of 20 ...
4
votes
3answers
512 views

What are the differences between notch filter & Goertzel?

I would like to integrate in my application a tone detector but I'm confused between 2 kinds of filters: Goertzel or Notch? I saw that Goertzel is a recommended for tone detection. But - what if I ...
4
votes
5answers
331 views

Determine when a constant signal changes to another constant value

As a novice to digital signal processing I have a scenario that probably seems trivial but I dont know the answer to. I want to detect when a signal changes but ignore noise. 255 255 255 255 255 ...
4
votes
3answers
1k views

How to Prove a System Is Invertible?

what i know is that for a system to be invertibel it should be one-one , but I am confused that if i am given a transfer function of a LTI system how can I prove or verify if it is invertible. ...
4
votes
3answers
2k views

Removing unwanted peaks from signal

I have a signal which looks something like: The 12 main round peaks is what I'd like to keep. However, the peak detection algorithm I apply is picking up the in-between noisy peaks. Any strategies I ...
4
votes
1answer
2k views

Generating good synchronization sequences

As part of my work I am putting together a simple bursty BPSK communication system. I want to make the demodulation easy, so I am going to put a synchronization sequence at the beginning of each ...
4
votes
1answer
2k views

Acoustic feedback detection algorithm

I am woking on an sound processing application where I have limited processing resources. I need to be able to detect acoustic feedback and then signal that such an event occurred. I am not concerned ...
4
votes
3answers
4k views

Pulse Compression(Chirp) SNR Gain

I've created both single tone signal and a LFM chirp signal with same pulse duration and cross correlated both of them with their own(matched filter). Peak points of both results were same as expected ...
4
votes
1answer
955 views

Radar Pulse Compression Gain (PCR)

Assume a monostatic radar is transmitting a pulsed waveform. The pulse has been modulated by a Barker code with$\ N$ chips or bits. The waveform chip rate is $\tau_c $, the radar receiver's detection ...
4
votes
2answers
892 views

Generating a signature to identify RF modulation types

Thanks to the Realtek 2832U I'm just discovering the world of Software Defined Radio. There are a lot of signals I'm able to pick up with this device, but identifying them is not always easy and ...
4
votes
3answers
4k views

How detect signal from noise?

I'm trying to detect when a signal is "on" from samples I have. Those samples come from a software defined radio, if that matters, and the signal i'm trying to detect is a WiFi signal. The problem is ...
4
votes
2answers
1k views

Thoretically, what makes multi-pitch detection so difficult?

For multi-pitch detection, I mean for example pressing several piano keys at the same time. For signal pitch detection (pressing one key at a time), after FFT, mostly the frequency with the largest ...
4
votes
1answer
248 views

How to detect underdamped harmonic signal?

I would like to ask what could be the easiest way to detect the presence and beginning (no more, no less) of under-damped harmonic signal in a collect of ultrasound data. I have some acquired data ...
4
votes
2answers
2k views

How to determine SNR from FFT of measured data?

I am doing impedance measurements, where I do a frequency sweep of a test current, and I measure the resulting voltage. Offline, I compute the FFTs of the voltage and current, and I want to make sure ...
4
votes
0answers
95 views

Finding the parameters and endpoints of a sinusoid

Suppose I have some signal $$ s(t) = n(t) + \left\{\begin{aligned} &0 &&: t < t_0\\ &A e^{i (2 \pi f t + \theta_0)} &&: t_0 \le t \le t_1\\ &0 &&: t > t_1 \...
3
votes
3answers
8k views

Window function and length of signal

I'm new to FFT and DSP and I want to ask you some questions about calculating FFT in Matlab. The following code is from Matlab help, I just removed the noise. What happens if I choose the length of ...
3
votes
2answers
335 views

Why does pulse-width modulation work?

When we apply pulse-width modulation (PWM) on controlling the brightness of a LED or the speed of a DC motor, is it the lag in our eyes that is responsible for the feeling of a continuous powering or ...
3
votes
1answer
370 views

What is the theoretical upperbound of information that could be transmitted by a device per second?

Suppose I would like to stream data from a device in a single second. What would be the theoretical upperbound of the amount of information (in bits, bytes, pixels...) that could be sent during this ...

1
2 3 4 5
7