sampling frequency


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sampling frequency

This article is provided by FOLDOC - Free Online Dictionary of Computing (foldoc.org)

sampling

(1) In statistics, the analysis of a group by determining the characteristics of a significant percentage of its members chosen at random.

(2) Converting analog signals into digital form. Audio and other analog signals are continuous waveforms that are analyzed at various points in time and converted into digital samples. The accuracy with which the digital samples reflect their analog origins is based on "sampling rate" and "sample size." See A/D converter.

Sampling Rate - When to Measure
The sampling rate is the number of times per second that the waveform is measured, which typically ranges from 8 to 192 thousand times per second (8 kHz to 192 kHz). The greater the rate, the higher the frequency that can be captured. For a comparison of high-quality samples, see high-resolution sampling rates.

The sampling rate must be at least twice that of the analog frequency being captured. For example, the sampling rate used to create the digital data on a CD is 44.1 kHz, slightly more than double the 20kHz frequency an average person can hear. The sampling rate for digitizing voice for a toll-quality conversation is typically 8,000 times per second (8 kHz), twice the 4 kHz required for the full spectrum of the human voice. See analog and Nyquist theorem.

Sample Size - The Measurement
Also called "resolution" and "precision," the sample size is the measurement of each sample point on a numeric scale. Known as "quantizing," the sample point is turned into the closest whole number. The more granular the scale (the more increments), the more accurate the digital sample represents the original analog signal. See oversampling, quantization and PCM.


Sampling Sound
The faster the sampling rate and the larger the sample size, the more accurately sound can be digitized. An 8-bit sample breaks the sound wave into 255 increments compared with 65,535 for a 16-bit sample.







Sampling Dialog
This recording dialog from an earlier Sound Blaster sound card shows typical sampling options for digitizing sound into Windows WAV files.







DSD - A High-Res Sampling Technique
Direct Stream Digital (DSD) is a dramatic departure from PCM. Instead of turning samples into a number with a range of values, DSD samples are only 1-bit long (0 or 1), depending on whether the wave is moving up or down from the previous sample point (see DSD).
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References in periodicals archive ?
Sampling frequency is 1 MHz (20,000 samples per period for 50 Hz mains).
Sampling frequency affects the processing of Actigraph raw acceleration data to activity counts.
Relationship among the resistance r, sampling frequency [f.sub.s], and [k.sub.at_critical] by the single update PWM and proposed method is shown in Figure 6.
As mentioned previously, one of the key achievements of this investigation is a system development for movement recognition using a sampling frequency around 10 Hz, which is up to ten times lower than the one used in novel studies.
The audio signal mostly has Sampling Frequency of about 32 kHz, 44.1 kHz, and 48 kHz.
Five tests of 30 seconds length were performed for each testing location using a sampling frequency of 400 Hz.
In all experiments, signals are sampled at the sampling frequency [f.sub.s] = 44.1 kHz over an acquisition time T =1 sec, so the number of samples acquired is N = 44100 samples, discrete Fourier transform (DFT) is computed with a 100000-point FFT, and the frequency increment is df = 1 Hz.
As shown in Figure 3, the architecture of the proposed sample-and-hold (S/H) circuit is consisted of an output feedback of operational transconductance amplifier (OTA); a hold capacitor and a switch operate at sampling frequency. The voltage at the terminals of the capacitor follows the voltage to convert when the switch is off, this is on one hand.
Fractal also can quantify unordered behavior and does not require the same pace between signal frequency and sampling frequency and does not need time-frequency transformation.
From this position on the spectrum is mirrored and repeats up to the sampling frequency. In Section 3, the symmetry of the DFT and its consequences are discussed in more detail.