Permissible noise norms, or how many decibels in ...? Noise Pollution: How to protect yourself? The ratio of the signal is 80 dB.

Amplifier - an indispensable attribute of high-quality sound in the car. And not only because of the power. First of all, the power supply provides music reproduction with minimal distortion. Therefore, if you strive for high quality and, of course, loud sound - You can't go without an amplifier.

Amplifiers: Let the "heart" of your acoustics sound louder!

Among the car owners there is an interesting comparison: the "brain" of the automotive speaker system is considered high-quality radio or multimedia, and "heart" - the best amplifiers.

Automotive acoustic amplifiers - These are devices designed to improve sound quality, increasing its power, cleanliness, spectrum and strength. At the exit after such treatment, you can hear high-quality and audience, which initially seemed to be "dim" and "lifeless."

These devices work as follows: the signal comes from standard magnetic To the columns or subwoofer, then passes through the amplifier and only then he comes to the ears of the car owner and its passengers. On how much "cut off" sound signalThe class of amplifiers will depend on:

· Analog - provide an output signal with a minimum number of distortion, do not reduce the amplitude of the sound;

· Digital - skip the signals through filters, retain the range, the width of the pulses, allow you to convey to hearing even the lowest frequencies.

How to choose amplifiers for autoacoustics?

The priority characteristic to pay consumers who want buy amplifiers, the price is considered. It depends not only on the brand, but also on the functionality of the device. For example, in addition in expensive models, there is an equalizer that is responsible for setting up the range. Often there are in devices and bass regulators that provide the quality of the sound of rhythmic and loud melodies.

Be sure to pay attention to the dimensions. Compact amplifiers will not take a lot of space in the cabin, will be invisible to look around. And modern design will make them an integral part of the interior.

And, of course, when choosing an amplifier, you must familiarize yourself with its power. The higher this parameter, the better the sound at the output. However, this may affect the amount of energy consumed.

the site presents the best amplifiers for you!

If you are looking for where buy Amplifiers for acoustics in Sevastopol, Check out the online store window store. For you - a wide selection of multifunctional devices, characterized in both dimensions and functionality and price. Famous manufacturers guarantee the durability of the acquired devices, and our store is their quality and excellent consumer properties.

We remind you that in the sitors you can use the free selection of devices and order the installation of the purchased goods.

In the last article we touched on the topic of cleaning with the ears with cotton chopsticks. It turned out that, despite the prevalence of such a procedure, the independent cleaning of the ears can lead to perforation (rupture) of the eardrum and a significant decrease in hearing, up to a complete deafness. However, the improper cleaning of the ears is not the only thing that can spoil our rumor. Excessive noise exceeding sanitary standards, as well as barotraums (injuries associated with pressure drop) can also lead to hearing loss.

In order to have an idea of \u200b\u200bthe danger, which noise is for hearing, you need to familiarize with the permissible noise standards for different days of day, and also to learn what level of noise in the decibelchs produce certain sounds. Thus, it is possible to begin to understand what is safe for hearing, and what is danger. And with understanding will come and the ability to avoid the harmful effects of sound on the rumor.

According to sanitary standards, a permissible level of noise, which does not harm hearing, even with long-term exposure to the auditory apparatus, it is customary to: 55 Decibel (DB) during the daytime and 40 decibel (dB) at night. Such values \u200b\u200bare normal for our ear, but, unfortunately, they are very often violated, especially within large cities.

Noise level in decibels (dB)

Indeed, often the normal level of noise is significantly exceeded. Here are examples of only some sounds that we face in our life and how many decibels (dB) in reality these sounds contain:

Spoken speech varies from 45 decibel (dB) to 60 decibel (dB), depending on the volume of the voice;
Automotive beep reaches 120 decibel (dB);
Noise of intensive traffic - up to 80 Decibel (dB);
Children's Plach - 80 Decibel (DB);
Noise of operation of a variety of office equipment, vacuum cleaner - 80 Decibel (dB);
Noise of the working motorcycle, trains - 90 Decibel (dB);
Sound of dance music in a nightclub - 110 Decibel (dB);
The noise of the flying aircraft - 140 Decibel (DB);
Noise of repair work - up to 100 Decibel (dB);
Cooking on the stove - 40 Decibel (dB);
Forest noise from 10 to 24 Decibel (dB);
Fatal for man noise level, explosion sound - 200 decibel (dB).

As you can see, most of the noise with which we face literally every day, significantly exceed the permissible threshold of the norm. And these are only natural noises with whom we cannot do anything. But there is still noise from the TV, loud music, which we ourselves expose our auditory apparatus. And imaginary harm to our rumor.

What level of noise is harmful?

If the noise level reaches 70-90 decibels (dB) and continues for quite a long time, then such noise with long-term exposure can lead to diseases of the central nervous system. A long-term impact of noise with a level of more than 100 decibels (dB) can lead to a significant reduction in hearing up to a complete deafness. Therefore, harm from speech music, we get much more than pleasure and benefits.

What happens with hearing when exposed to noise?

Aggressive and long-term noise effect on the hearing apparatus can lead to perforation (rupture) of the eardrum. The consequence of this is a decrease in hearing and, as an extreme case, a complete deafness. And although the perforation (break) of the eardrum is a reversible disease (i.e., the drumpoint can recover), but the recovery process is long and depends on the severity of perforation. In any case, the treatment of perforation of the eardrum is under the supervision of a doctor who chooses a treatment regimen after inspection.

The ratio of pure audio signal to noise created by the device itself.

The value above (in dB), the better.

Sound Blaster X-Fi sound card is a signal / noise value - 118 dB.

Most audio codecs - 80-95 dB.

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2014-03-08T21: 22.

Audiophile "S Software

Introduction

Usually noise is much better heard when using headphones than when using columns, and is a popular complaint with headphone owners.

There are many misconceptions about where the noise, characteristics and methods of its comparison come from.

What is noise?

Technically, noise is everything except the useful signal. Usually we are interested in noises only in the range of 20 Hz to 20 kHz. Inside this range ear more sensitive to one frequencies than to others. The most common audible noise by nature is completely occasionally perceived as broadband hiss. The low-frequency buzz at the frequencies of the power supply network (50 or 60 Hz) can also be heard. All digital devices, especially computers and cell phonescan create noise at certain frequencies, perceived as creak, click, hum, etc.

Sources of noise

An audible noise may occur, and often occurs in the signal tract, starting from the microphone recording. Here are the most common sources:

Sound recording - Microphone preamplifiers and other equipment used during recording often contributes audible noise. But there are many technologies used to reduce their hearing. Noise reduction (English Noise Gate), for example, is used to exclude noise to the moments when there is no useful signal (from a microphone or tool). Almost all the records made before the beginning of the 80s were masters using an analog film that makes a significant hiss. And even digital records may contain a noise made by electronics during the transmission and signal processing process. Also, by itself, the high level of noise has vinyl.

DAC - Theoretically, the ideal 16-bit DAC has a signal-to-noise ratio of 96 dB, but some DACs are not reached to maximum 16-bit formats. 24-bit DACs usually have the accuracy of the corresponding 16 bits, the best of them Barely reach 21 bits (effective number of binary discharges). In particular, it concerns the DAC embedded in PC. Some DACs also make a large amount of own noise - intermodulation, quantization noise (although they can be considered as distortion, as they take place only if there are useful signal).

Amplifier - Even a netbook or a portable player has a built-in power amplifier for headphones (in some cases it is already included in the DAC chip). Any amplifier makes noise, the only question is, this noise is heard, or not. Even the most expensive external headphone amplifiers can make a significant amount of noise. In addition, of course, noises enhanced by the amplifier input along with the signal.

Noise accumulate - Although sometimes a certain main source of noise is obvious, noise can also be made equally to several components. In this case, noises are summed up.

Measures noise

Example

Noise in DBV at 100% volume - -112 DBV Unweighted and -115 DBV A-Weighted

Signal / noise relative to the maximum output - 130 DBR UNWEIGHTED and -133 DBR A-Weighted relative to 7 in the RMS maximum. These figures are impressive, but far from reality, as someone is unlikely to need a value at the exit close to 7 V.

Headphone sensitivity

Headphones differ significantly among themselves. Many believe that an increase in sensitivity by 10 dB will also worsen the signal-to-noise ratio of 10 dB, but it is often untold. Since the headphones are more sensitive, a smaller level of amplification and / or a smaller volume level is needed. In both cases, the noise level is reduced, because ratio The signal and noise available at the inlet of the amplifier remains unchanged. Only fixed noise is directly related to headphone sensitivity. Heat noise Volume controller can also complicate the situation, but as the sensitivity of the headphones grow, the importance of the level of fixed noise is growing (see above about the limit conditions).

Sometimes you can see the spectral analysis of noise. The average noise threshold on these graphs is much smaller than the noise specified in the characteristics. In the figure on the right, the total noise is approximately -112 dBv, but on the chart the noise lies at -150 dBv. The reason for such a big difference is that -112 DBV is the sum of noise components in the range of 20 Hz to 20 kHz. Imagine that you scattered a glass of sugar on the floor. This will slightly change the floor level. But if you gather all the sugar into the measuring tank, you can determine how much sugar is all - the indicators in the windows are also working.

Frequency range of noise. Weighing

Usually noise is the sum of power in the sound band. Ideally, the frequency band is indicated for unbelievable measurements. Weighing by type A (A-Weighting) is often used to adapt the results to the features of human hearing (different hearing sensitivity at different frequencies), it also limits the frequency band. Another weighing standard is ITU-R 468. For equipment that has a tendency to large quantity ultrasound noise, like amplifiers class D and digital equipment, Sometimes additional broadband noise measurements can be useful, up to 100 kHz.

Comparison of noise testimony

You can only directly compare readings in DBU, DBV or DBR, with the same level. All measurements should be used same range Frequencies and the same type of weighing. Otherwise, you will not be able to compare the results without performing some additional calculations, or they can not be compared in principle. Here are some examples:

RMAA - Unfortunately, the concept of RightMark Audio Analyzer is missing the concept of absolute values. Therefore, the program cannot calculate the noise level of relative to some specified value. She is trying to calculate dynamic range In DBFS, but these results are subjective and can vary depending on the device settings (volume level, recording level, etc.), calibration and so on. In general, the measurements of noise characteristics with RMAA are rarely accurate, and the eating noise of the PC equipment is often greater than what you want to measure. Some parameters analyzed by RMAA are actually present there "for a tick", and this is one of them.

dBV and DBR - If the device A has a noise level -100 dBv, and the device B - -108 DBR (support level 10 V), at first glance, it seems that the noise of the device B is 8 dB less. But for A, the value is indicated in relation to 1 V, and for B - to 10 V. The difference is 20 * log (10/1) \u003d 20 dB. So in reality for B with respect to 1 to the level will be 20 dB above, that is, -88 dBv. See the basic transformations below.

dBU in DBV - These values \u200b\u200bare similar. To convert from DBV in DBU, reduce the value module by 2.2 dB. For reverse conversion, increase the module for 2.2 dB.

dBR (400 mV) in DBV - I updated the results of my own measurements, converting DBR with a reference level of 400 mV to DBV (support level 1 V). For such a conversion, the module value must be increased by 8 dB (for reverse - reduce).

Basic transformations - The essence is to add or subtract 20 * log (VREF1 / VREF2) dB. The lower the reference level, the greater the relative indicator of noise. Also, the level can be set in relation to power (instead of voltage). In this case, the value is calculated as 10 * log (Pref1 / Pref2).
- dBV in Volta - 10 ^ (dBV / 20)
- -96 dB in volts - 10 ^ (- 96/20) \u003d 16 μV (0.000016 V)
- Volta in DBV \u003d 20 * log (B)

Various types of weighing - It is impossible to accurately compare the values \u200b\u200bthat are poured using various weighing, since they depend on the frequency distribution of noise. For example, an amplifier with a significant level of hum will have a smaller weighted value of noise than an amplifier with a uniformly distributed noise. In most cases, however, it should be expected that weighing by type A will give a noise level by 3-6 dB below than non-invisible.

Impedance source

Thermal noises are often the main source of noise in preamstressors and amplifiers for headphones. And they are proportional to the impedance of the input circuit, which also includes a source. The higher the impedance of the source, the more noise. For example, an amplifier for headphones works properly from the source with an impedance of 100 ohms, but the use of an impedance source 10 kΩ can easily lead to audible noise. IN this case Noises that you hear are in reality produced by the input device, not an amplifier..

Noise measurement

Since the noise level value is the sum of the components in the sound frequency range, and is also usually very low, it is accurate - very problematic. The best high-end equipment for the PC can have a fairly low noise shelf, but at the same time rarely allows you to measure when maximum meaning At the output of the device. And, more importantly, sound equipment The PC does not allow to establish an absolute value - in B, dBv, etc. only a few digital multimeters have sufficient resolution and a sufficiently low level of own noise for measurements with an accuracy of MKV in the range of 20-20000 Hz. Theoretically, you can temporarily calibrate 24-bit sound cardUsing the exact measuring device and the corresponding test signals. But here there are many nuances depending on the software used. The source impedance is also a problem. The developers prefer when measured to slow down the input contacts of the device to obtain the best noise indicators, however, closest to real results can be obtained by connecting the shunt resistance close to the impedance of a typical source. If you try to use a real source, its noises will be included in the measurement result (as in the case of RMAA). When testing the DSC, you must use signals very low levelSince if there is nothing to file anything at all, it will completely turn off and show the results that do not correspond to reality. Almost any high-quality sound analyzer will be able to exclude this low-level signal from the results, leaving only noise.

Measurements with RMAA

Even if you managed to calibrate the levels, you still do not know which conversions occur within the RMAA program. This is a magical "black box", without any trustworthy documentation describing how the program calculates the output values. What frequency range was used? Is the result weighted or unbelievable? Plus to everything, the results of the noise of the equipment used in the results are included. Eventually, best way Measure noise is to use Audio Precision and Prism Sound analyzers.

Conclusion

Noise at -105 DBV (with respect to 1 c) almost always turn out to be inappropriate. The level of noise in the area of \u200b\u200b-95 DBV is acceptable for most listeners. Noise level values \u200b\u200bspecified in other values \u200b\u200bmust be previously converted to DBV or similar units before they can be compared. The results obtained using RMAA are usually non-informative, since it is impossible to determine the absolute values. RMAA can only define a dynamic range, and it is not always, since it is often difficult to properly adjust the levels without special equipment.

Original Article in English: Noise & Dynamic Range

What is noise, how to measure it in which values. What is a dynamic range, and what it differs from the noise level.

The main causes of low noise characteristics

The main reasons for the high noise level in signal systems:

If the useful signal spectrum differs from the noise spectrum, improve the signal-to-noise ratio can be limited to the system bandwidth.

To improve the noise characteristics of complex complexes, electromagnetic compatibility methods are used.

Measure

In the audio engineering, the signal-to-noise ratio is determined by measuring the noise voltage and signal at the output of the amplifier or other sound reproducing device with a rms of mean-square minivololtmeter or the spectrum analyzer. Modern amplifiers and other high-quality audio equipment has a signal / noise indicator of about 100-120 dB.

In systems with higher demands, indirect methods of measuring signal-to-noise ratio implemented on specialized equipment are used.

In music

The signal-to-noise ratio is the actual speaker amplifier parameter, shows how much the amplifier is noisy (from 60 to 135.5 dB), if in the absence of the signal to unscrew the volume control to the maximum. The greater the signal / noise value, the more clean sound provide columns. It is desirable that this parameter is at least 75 dB for powerful speakers with high-quality sounding at least 90 dB.