How to measure signal-to-noise ratio. Measurements
The ratio of the clean audio signal to the noise generated by the device itself.
The higher the value (in dB), the better.
The Sound Blaster X-Fi sound card has a signal-to-noise value of 118 dB.
Most audio codecs have 80-95 dB.
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Notes or textbook covering signal-to-noise ratio, SNR, signal-to-noise ratio measurements, and signal-to-noise ratio formulas.
Noise characteristics and, consequently, signal-to-noise ratio are key parameters for any radio receiver. Signal-to-noise ratio, or SNR as it is often called, is a measure of the sensitivity of a receiver. This is of paramount importance for all applications, from simple radio transmitting devices to those used in cellular or wireless communications, as well as in fixed or mobile radiotelephone communications, two-way radio communications, satellite communications systems and many others.
There are a number of ways in which the noise signature, and therefore the sensitivity, of a radio receiver can be measured. The most obvious method is to compare signal and noise for a known signal level, i.e. signal-to-noise ratio (S/N) or SNR. Obviously, the greater the difference between the signal and the unwanted noise, i.e., the greater the S/N ratio or SNR, the better the sensitivity of the radio receiver.
As with any sensitivity measurement, the performance of the radio receiver as a whole is determined by the performance of the final amplifier stage. Any noise that arrives at the input of the first stage of the RF amplifier will be summed with the signal and amplified in subsequent amplification stages of the receiver. In the case when the noise entering the first stages of the RF amplifier will be amplified to the greatest extent, this AMP will become the most critical, from the point of view of receiver sensitivity, in terms of performance. Thus, the first amplifier of any radio must be low noise.
Concept of signal-to-noise ratio SNR.
Although there are many ways to measure the sensitivity of a radio receiver, C/N ratio or SNR is one of the simplest and is used in a variety of applications. However, it has a number of limitations and although it is widely used, other methods, including noise figure, are also often used. However, S/N ratio or SNR is an important indicator and a widely used measure of receiver sensitivity.
The difference is usually defined as the signal to noise ratio (S/N) and is usually expressed in decibels. Since the input signal level obviously has an influence on this ratio, the input signal level must be known. It is usually expressed in microvolts. Typically, a certain input signal level is required to achieve a signal-to-noise ratio of 10 dB.
Signal-to-noise ratio formula
Signal-to-noise ratio is the ratio between the desired signal and the unwanted interfering noise.
It is more common to see the signal-to-noise ratio expressed in logarithmic units using decibels:
If all components are expressed in decibels, then the formula can be simplified to:
The power value can be expressed in levels such as dBm (decibel relative to milliwatt or some other value whose levels can be compared).
Effect of Bandwidth on SNR
A number of other factors, in addition to the main indicators, can affect the signal-to-noise ratio, SNR. The first factor is the actual bandwidth of the receiver. Since noise spreads over the entire frequency range, we found that the wider the receiver bandwidth, the higher the noise level. Accordingly, the receiver bandwidth must be determined.
In addition, it was found that the use of amplitude modulation affects the level of modulation. The higher the modulation level, the higher the audio signal at the receiver output. When measuring the noise level, the audio output signal of the receiver is also measured and, accordingly, the level of AM modulation is affected.
Typically a modulation factor corresponding to 30% is selected for this measurement.
Signal to Noise Ratio Specification
This method of measuring efficiency is most often used for RF receivers. Typically, you can expect an S/N ratio figure in the region of 0.5 µV per 10 dB bandwidth of 3 kHz with OBP or Morse. For AM, you can expect an S/N ratio of 1.5 µV at 10 dB and a bandwidth of 6 kHz at a modulation level (AM) of 30%.
What to pay attention to when measuring signal-to-noise ratio
SNR is a very convenient way to quantify receiver sensitivity, but there are some points to consider when interpreting and measuring signal-to-noise ratio. When investigating this, it is necessary to pay attention to the way the signal-to-noise ratio, SNR, is measured. A calibrated RF signal generator is used as a signal source for the receiver. It must have a precise method for adjusting the output level to very low signal levels. Then, at the receiver output, a universal AC voltmeter is used to measure the output signal level. S/W and (S+W)/W.
When measuring signal-to-noise ratio, there are two main measurement quantities. One is the noise level and the other is the signal level. As a result of the way the measurements are made, often the measurement of the wanted signal also includes noise, i.e. it is a signal + noise measurement. This is generally not too much of a problem since the signal level is expected to be much higher than the noise level. In this regard, some receiver manufacturers will indicate a slightly different ratio: namely signal and noise to noise (S+N)/N. In practice, the difference is not big, but the ratio (S+W)/W is more correct. Sometimes the specification of a signal generator mentions that it is either a voltage difference generator or an EMF generator. This is actually very important because there is a 2:1 ratio between the two levels. For example, 1 µV EMF and 0.5 µV RP are the same. EMF (electromotive force) is the open circuit voltage of the generator, while DP (potential difference) is measured when the generator is loaded. The result of the way the oscillator circuit operates assumes that a real load (50 ohms) is applied. If the load is not equal to this value, an error will occur. Regardless, most equipment will take PP values unless otherwise specified.
Although there are many parameters that are used to indicate the sensitivity characteristics of radio receivers, the signal-to-noise ratio is one of the most basic and easily understood. Therefore, it is widely used for various radio receivers used in applications ranging from radio reception to fixed or mobile radio communications.
Main reasons for low noise performance
The main reasons for high noise levels in signaling systems are:
If the spectrum of the desired signal differs from the spectrum of the noise, the signal-to-noise ratio can be improved by limiting the system bandwidth.
To improve the noise characteristics of complex systems, electromagnetic compatibility methods are used.
Measurement
In audio engineering, the signal-to-noise ratio is determined by measuring the noise voltage and signal at the output of an amplifier or other sound-reproducing device with an rms millivoltmeter or spectrum analyzer. Modern amplifiers and other high-quality audio equipment have a signal-to-noise ratio of about 100-120 dB.
In systems with higher requirements, indirect methods for measuring the signal-to-noise ratio are used, implemented on specialized equipment.
In music
The signal-to-noise ratio is a parameter of the amplifier of active speakers; it shows how much noise the amplifier makes (from 60 to 135.5 dB) if, in the absence of a signal, the volume control is turned to maximum. The higher the signal-to-noise value, the clearer the sound the speakers provide. It is desirable that this parameter be at least 75 dB; for powerful speakers with high-end sound, at least 90 dB.
In the video
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Wikimedia Foundation.
- 2010.
- Barricades (software)
Larynx
See what “signal-to-noise ratio” is in other dictionaries:- Signal to Noise Ratio (SNR, Signal to Noise Ratio) is a dimensionless quantity equal to the ratio of the useful signal power to the noise power. Usually expressed in decibels. The higher this ratio, the less noticeable the noise. where P is the average... ... Wikipedia
signal-to-noise ratio- The ratio of the amplitude (or energy) of the signal created by a defect in a material to the root mean square value of the signal (or energy) of the noise. [Non-destructive testing system. Types (methods) and technology of non-destructive testing. Terms and Definitions …
signal-to-noise ratio- - [Ya.N.Luginsky, M.S.Fezi Zhilinskaya, Yu.S.Kabirov. English-Russian dictionary of electrical engineering and power engineering, Moscow, 1999] Topics of electrical engineering, basic concepts EN signal to noise ratioS/N ratio ... Technical Translator's Guide
signal-to-noise ratio- (ITU T G.691; ITU T G.983.2 G.991.2). Technical Translator's Guide
Topics: telecommunications, basic concepts EN signal to noise ratioSNR... Signal to noise ratio G/s d
signal-to-noise ratio- a value characterizing the change in the gradient G against the background of the optical density of an equally exposed radiographic image. Source … - 3.4 signal-to-noise ratio: The ratio of the ultrasonic signal level to the “background” noise level, expressed in decibels (dB). Source …
signal-to-noise ratio Dictionary-reference book of terms of normative and technical documentation
- signalo ir triukšmo santykis statusas T sritis automatika atitikmenys: engl. signal to noise ratio vok. Signal/Rausch Verhältnis, n rus. signal-to-noise ratio, n pranc. rapport signal/bruit, m … Automatikos terminų žodynas Technical Translator's Guide
signal-to-noise ratio in magnetic testing signal-to-noise ratio in magnetic non-destructive testing Technical Translator's Guide
- signal-to-noise ratio The ratio of the peak value of the magnetic transducer signal, caused by a change in the measured characteristic of the magnetic field, to the root mean square value of the noise amplitude caused by the influence of interfering parameters... ... integrated circuit signal-to-noise ratio Technical Translator's Guide
- signal-to-noise ratio The ratio of the effective value of the output voltage of an integrated circuit containing only low-frequency components corresponding to the frequencies of the modulating voltage to the effective value of the output voltage at ... Let’s be clear right away that we’re discussing gaps here., and not “logic”, i.e. breaks with loss of carrier. The biggest influence on the quality of communication is determined by the cable from the telephone exchange to the distribution network (Distribution Box - located on the staircase in the panel, usually above switches and electricity meters). Moreover, not only the quality and length of this cable (distance from the telephone exchange) affects, but also the conditions in which they are laid. There is no point in listing everything, there are many of them - from filled wells to the cable from the intercom at the entrance. These are all things that you cannot change, i.e. if the problem is THIS section, then most likely, after you wear out the caliper, they will write you a technical failure. Now here's what you can do yourself to diagnose the problem:
0.
a) Take a hammer.
b) Place your USB modem on a stool.
c) make sure that people are not harmed during the swing.
d) Hit the center of the box three times.
e) Collect the fragments and throw them in the trash.
Dear, do not buy USB modems. The use of half-software devices with buggy, ever-flying drivers and connecting via USB, which the system, “to save energy,” cuts off for a second is at least not logical when the cost of NORMAL routers is within 1k rubles.
1. Check the connection diagram. Everything is simple here. I hope there is no need to explain the diagram. Are there any breaks? Check the functionality of the splitter (read: try with another one), and exclude ALL unfiltered devices using the telephone network (Caller ID, fax, dial-up modem, etc.). Also check the wiring for twists, solders, breaks, or damage to the insulation. Avoid contact with the outlet or the presence of capacitors in it. We also try to disconnect all devices from the line, and connect the modem directly to the telephone socket (if there are several, to each). Try changing the wires from the modem to the splitter and from the splitter to the line. The line parameters (more on them below) change over time, and not for the better. In other words, if there are no complaints about the quality of telephone communication, this does not mean that oxidation of the telephone line, for example (which, by the way, can occur in any area, right up to the telephone exchange) did not affect you. It may still be at an early stage. At a later stage, a crackling sound appears and noises arise.
2. Diagnostics of linear indicators. Important indicators of a telephone line for adsl are the noise level (Noise margin or SNR ratio) and attenuation level (Attenuation Line). They can be viewed in the router settings, usually located in the Status menu. Sample table of values:
Signal attenuation:
from 5dB to 20dB - the line is excellent.
from 20dB to 30dB - the line is good.
from 30dB to 40dB - the line is bad.
from 50dB and above the line is very bad.
Margins (signal to noise ratio):
6dB and below sucks, ADSL may not work
7dB-10dB average, if worsened, instability may occur.
11dB-20dB is good
20dB-28dB excellent
29dB or more - super
Accordingly, we look and draw conclusions. We connect the modem directly without a splitter and SLT and again draw conclusions. If everything is also bad, then we connect from the distribution board. boxes, i.e. We physically remove the old cable going into the apartment and connect it with a short cable from the marks in the rk to the modem. then we measure the “margins” again.
Look carefully at the signal-to-noise ratio, it’s very bad if it is not stable but “floating”, that is, you have 15/20 up/down, and after 10 minutes 9/14. If the SNR “sags,” then the problem is probably in bad contacts along the entire section from the modem to the radio. It's worth checking more closely. All devices emitting electromagnetic waves also have a significant effect, such as dect phones, the bases of which are placed next to the modem. IT'S WORTH REMEMBERING - no unnecessary devices near the modem.
It’s also worth keeping a close eye on the clean people who try to rip out the wires and walk over them with a mop. It is also better to keep equipment for laundries and dry cleaners away from the modem - water will not lead to anything good, unless of course you have professional equipment from the company http://continent.com.ua/, which you should not doubt. For example, it is quite possible to keep a high-speed washing machine at home.
3. Changes in physical education. FIZLINK - channel capacity between the modem and the telephone exchange (dslam), i.e. physical connection speed. We won't go into details. We will go into only one detail - the higher the channel speed, the more errors and, as a rule, disconnects, etc. and so on. Sorry for the “handicraft” explanation, if you wish, you can “Google” and find out more. You need to realistically assess the capabilities of your line before asking to raise your physical link, especially since most people don’t need it. To set the optimal channel speed, you should contact the technical support service (8-125 for Rosstelecom subscribers) and together try to select a profile that matches your capabilities/desires.
4. Checking the modem. It goes without saying that the reason for the breaks may be the modem. about the usb modem was mentioned in paragraph zero. Also, if you have been using a modem for 3-4 years, it makes sense to try with a different modem. A sign of a “dying” modem is noise in the phone and the margin slowly “sliding” down. Check.
5. Mysticism. Cats running on modems and a veteran's grandfather's military radio station have long become classics of the genre. In general, you have a 1/1000 chance of ending up in the anomaly zone and then... in general, it’s worth taking into account.
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Signal to noise ratio(SNR; English signal-to-noise ratio, abbreviated SNR) - a dimensionless quantity equal to the ratio of the useful signal power to the noise power.
S N R = P s i g n a l P n o i s e = (A s i g n a l A n o i s e) 2 (\displaystyle \mathrm (SNR) =(P_(\mathrm (signal) ) \over P_(\mathrm (noise) ))=\left((A_( \mathrm (signal) ) \over A_(\mathrm (noise) ))\right)^(2))Where P- average power, and A- root mean square amplitude value. Both signals are measured within the system bandwidth.
Typically, signal-to-noise ratio is expressed in decibels (dB). The larger this ratio, the less noise affects system performance.
S N R (d B) = 10 log 10 (P s i g n a l P n o i s e) = 20 log 10 (A s i g n a l A n o i s e) (\displaystyle \mathrm (SNR(dB)) =10\log _(10)\left(( P_(\mathrm (signal) ) \over P_(\mathrm (noise) ))\right)=20\log _(10)\left((A_(\mathrm (signal) ) \over A_(\mathrm (noise ) ))\right))
Main reasons for low noise performance
Performance Improvement Methods
Reducing the inherent noise of the amplification path (low-noise amplifiers) is achieved by appropriate circuit solutions, in particular the use of active and passive components with low noise levels.
If the spectrum of the desired signal differs from the spectrum of the noise, the signal-to-noise ratio can be improved by limiting the system bandwidth.
To improve the noise characteristics of complex systems, electromagnetic compatibility methods are used.
Measurement
In audio engineering, the signal-to-noise ratio is determined by measuring the noise voltage and signal at the output of an amplifier or other sound-reproducing device with an rms millivoltmeter or spectrum analyzer. Modern amplifiers and other high-quality audio equipment have a signal-to-noise ratio of about 100-120 dB.
In systems with higher requirements, indirect methods for measuring the signal-to-noise ratio are used, implemented on specialized equipment.
In audio engineering
Signal-to-noise ratio - parameter of ADC, DAC, mixer, microphone, pre-amplifier or final amplifier, for example
