Signal to noise ratio 80 dB. Permissible noise standards, or how many decibels in...? Comparison of noise readings

In the last article we touched on the topic of cleaning ears with cotton swabs. It turned out that, despite the prevalence of such a procedure, self-cleaning of the ears can lead to perforation (rupture) of the eardrum and a significant decrease in hearing, up to complete deafness. However, improper ear cleaning is not the only thing that can damage our hearing. Excessive noise that exceeds sanitary standards, as well as barotrauma (injuries associated with pressure changes) can also lead to hearing loss.

To have an idea of ​​the danger that noise poses to hearing, it is necessary to familiarize yourself with the permissible noise standards for different times of the day, as well as find out what noise level in decibels certain sounds produce. In this way, you can begin to understand what is safe for your hearing and what is dangerous. And with understanding comes the ability to avoid the harmful effects of sound on hearing.

According to sanitary standards, permissible noise levels that do not harm hearing even with prolonged exposure hearing aid, it is generally accepted: 55 decibels (dB) during the day and 40 decibels (dB) at night. Such values ​​are normal for our ear, but, unfortunately, they are very often violated, especially within large cities.

Noise level in decibels (dB)

Indeed, the normal noise level is often significantly exceeded. Here are examples of just some of the sounds we encounter in our lives and how many decibels (dB) these sounds actually contain:

  • Spoken speech ranges from 45 decibels (dB) to 60 decibels (dB), depending on the volume of the voice;
  • Car horn reaches 120 decibels (dB);
  • Heavy traffic noise – up to 80 decibels (dB);
  • Baby crying – 80 decibels (dB);
  • Operation noise of various office equipment, vacuum cleaner - 80 decibels (dB);
  • Noise of a running motorcycle, train - 90 decibels (dB);
  • The sound of dance music in a nightclub is 110 decibels (dB));
  • Airplane noise - 140 decibels (dB);
  • Noise from repair work – up to 100 decibels (dB);
  • Cooking on a stove - 40 decibels (dB);
  • Forest noise from 10 to 24 decibels (dB);
  • Lethal noise level for humans, explosion sound - 200 decibels (dB)).

As you can see, most of the noises that we encounter literally every day significantly exceed the permissible threshold. And these are just natural noises that we cannot do anything about. But there is also noise from TV and loud music, to which we expose our hearing aids. And with our own hands we cause enormous harm to our hearing.

What noise level is harmful?

If the noise level reaches 70-90 decibels (dB) and continues for quite a long time, then such noise with prolonged exposure can lead to diseases of the central nervous system. And prolonged exposure to noise levels of more than 100 decibels (dB) can lead to significant hearing loss, including complete deafness. Therefore, we get much more harm from loud music than pleasure and benefit.

What happens to hearing when exposed to noise?

Aggressive and prolonged noise exposure to the hearing aid can lead to perforation (rupture) of the eardrum. The consequence of this is decreased hearing and, as an extreme case, complete deafness. And although perforation (rupture) of the eardrum is a reversible disease (i.e., the eardrum can recover), the recovery process is long and depends on the severity of the perforation. In any case, treatment of perforation of the eardrum is carried out under the supervision of a doctor, who chooses a treatment regimen after examination.

Amplifier is an indispensable attribute high-quality sound in the car. And not just because of the power. First of all, the power reserve ensures music playback with minimal distortion. Therefore, if you strive for high-quality and, of course, loud sound, you cannot do without an amplifier.

Amplifiers: let the “heart” of your acoustics sound louder!

There is an interesting comparison among car owners: the “brain” of the car speaker system A high-quality radio or multimedia is considered, and the “heart” is the best amplifiers.

Car audio amplifiers- These are devices designed to improve sound quality, increasing its power, purity, spectrum and strength. At the output after such processing, you can hear a high-quality audio recording that initially seemed “dull” and “lifeless.”

These devices work as follows: the signal comes from the standard radio to the speakers or subwoofer, then passes through an amplifier and only then does it reach the ears of the car owner and his passengers. On how much it is “cut off” sound signal, the class of amplifiers will also depend:

· analog – provide an output signal with a minimum amount of distortion and do not reduce the sound amplitude;

· digital – pass signals through filters, preserve the range and pulse width, and allow even the lowest frequencies to be heard.

How to choose amplifiers for car audio?

The primary characteristic that consumers who want to pay attention to buy amplifiers, the price is considered. It depends not only on the brand, but also on the functionality of the device. For example, expensive models additionally provide an equalizer that is responsible for adjusting the range. Devices often have bass controls that provide sound quality for rhythmic and loud melodies.

Be sure to pay attention to the dimensions. Compact amplifiers will not take up much space in the cabin and will be invisible to others. A modern design will make them an integral part of the interior.

And, of course, when choosing an amplifier, you need to familiarize yourself with its power. The higher this parameter, the higher quality the output sound will be. However, this may affect the amount of energy it consumes.

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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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2014-03-08T21:22

2014-03-08T21:22

Audiophile's Software

Introduction

Noise is generally much more audible when using headphones than when using speakers, and is a popular complaint among headphone owners.

There are many misconceptions about where noise comes from, its characteristics, and how to compare it.

What is noise?

Technically, noise is everything other than the useful signal. Typically we are only interested in noise in the range from 20 Hz to 20 kHz. Within this range, the ear is more sensitive to some frequencies than others. The most common audible noise is completely random in nature and is perceived as a broadband hiss. A low-frequency hum at mains frequencies (50 or 60 Hz) can also sometimes be heard. All digital devices, especially computers and Cell phones, may create noise on certain frequencies, perceived as creaking, clicking, humming, etc.

Sources of noise

Audible noise can, and often does, occur in the signal path, starting with the microphones used for recording. Here are its most common sources:

  • Sound recording- Microphone preamps and other equipment used during recording often introduce audible noise. But there are many technologies used to reduce their audibility. Noise Gate, for example, is used to eliminate noise when there is no useful signal (from a microphone or instrument). Almost all recordings made before the early 80s were mastered using analog tape, which introduces significant hiss. And even digital recordings can contain noise introduced by electronics during signal transmission and processing. Also, of course, vinyl has a high noise level.

  • DAC- a theoretically ideal 16-bit DAC has a signal-to-noise ratio of 96 dB, but some DACs do not reach the maximum performance of the 16-bit format. 24-bit DACs usually have an accuracy corresponding to only 16 bits, but the best ones barely reach 21 bits (the effective number of binary bits). This is especially true for DACs built into PCs. Some DACs also introduce a large amount of their own noise - intermodulation, quantization noise (although this can be considered as distortion, since it only occurs when there is a useful one). signal).

  • Amplifier- Even a netbook or portable player has a built-in headphone power amplifier (in some cases it is already included in the DAC chip). Any amplifier introduces noise, the only question is whether this noise is audible or not. Even the most expensive external headphone amplifiers can introduce a significant amount of noise. In addition, of course, the noise coming to the amplifier input along with the signal is amplified.

  • Noises accumulate- Although sometimes a primary source of noise is obvious, noise can also be contributed equally by multiple components. In this case, the noises are summed up.

Noise measurements

Example

  • Noise in dBV at 100% volume- –112 dBV unweighted and –115 dBV A-Weighted

  • Signal/noise relative to maximum output- 130 dBr unweighted and –133 dBr A-Weighted relative to 7 V RMS maximum. These figures are impressive, but far from reality, since it is unlikely that anyone will need an output value close to 7 V.

Headphone sensitivity

Headphones vary significantly in sensitivity. Many people believe that increasing sensitivity by 10 dB will also degrade the signal-to-noise ratio by 10 dB, but this is often not true. Since headphones are more sensitive, lower gain levels and/or lower volume levels are needed. In both cases, the noise level is also reduced, because ratio signal and noise present at the amplifier input remains unchanged. Only fixed noise has a direct bearing on the sensitivity of the headphones. Thermal noise from the volume control can also complicate things somewhat, but as the sensitivity of the headphones increases, the importance of the fixed noise level increases (see above about limiting conditions).

Sometimes you can see a spectral analysis of the noise. The average noise floor in these graphs is much lower than the noise specified in the specifications. In the figure on the right, the total noise is approximately -112 dBV, but in the graph the noise is at -150 dBV. The reason there is such a big difference is that –112 dBV is the sum of the noise components in the range from 20 Hz to 20 kHz. Imagine that you spilled a glass of sugar on the floor. This will change the floor level somewhat. But if you collect all the sugar in a measuring container, you can determine how much sugar there is in total - the indicators in the windows in the figure work the same way.

Frequency range of noise. Weighing

Typically, noise is the sum of the powers in the audio frequency band. Ideally, the frequency bandwidth is specified for unweighted measurements. A-weighting is often used to adapt results to the characteristics of human hearing (different hearing sensitivities at different frequencies), and it also limits the frequency bandwidth. Another weighing standard is ITU-R 468. For equipment that tends to a large number ultrasonic noise, such as Class D amplifiers and digital equipment, additional broadband noise measurements, up to 100 kHz, can sometimes be useful.

Comparison of noise readings

You can directly compare readings only in dBu, dBV or dBr, at the same level. All measurements must use the same frequency range and the same type of weighting. Otherwise, you will not be able to compare the results without performing some additional calculations, or they will not be comparable at all. Here are some examples:

  • R.M.A.A.- Unfortunately, the concept of RightMark Audio Analyzer lacks the concept of absolute values. Therefore, the program cannot calculate the noise level relative to a certain set value. It attempts to calculate dynamic range in dBFS, but these results are subjective and may vary depending on device settings (volume level, recording level, etc.), calibration, etc. In general, measurements noise characteristics RMAAs are rarely accurate, and the inherent noise of the PC hardware is often larger than what you want to measure. Some parameters analyzed by RMAA are, in fact, there “for show,” and this is one of them.

  • dBV and dBr- If device A has a noise level of –100 dBV and device B has a noise level of –108 dBr (10 V reference level), at first glance, device B appears to be 8 dB less noisy. But for A the value is given in relation to 1 V, and for B - to 10 V. The difference is 20*Log(10/1) = 20 dB. So in reality for B relative to 1 V the level will be 20 dB higher, i.e. -88 dBV. See basic conversions below.

  • dBu to dBV- These meanings are similar. To convert from dBV to dBu, reduce the magnitude of the value by 2.2 dB. For reverse conversion, increase the module by 2.2 dB.

  • dBr (400 mV) to dBv- I have updated my own measurements by converting dBr with a 400 mV reference level to dBV (1 V reference level). For such a conversion, the value module must be increased by 8 dB (for the reverse, reduced).

  • Basic Conversions- The idea is to add or subtract 20 * Log(Vref1 / Vref2) dB. The lower the reference level, the greater the relative noise figure will be. The level can also be set in relation to power (instead of voltage). In this case the value is calculated as 10 * Log (Pref1 / Pref2).
    • dBV to Volts - 10^(dBV / 20)
    • –96 dB to Volts - 10^(–96/20) = 16 µV (0.000016 V)
    • Volts in dBV = 20 * log (V)

  • Various types of weighing- It is not possible to accurately compare values ​​obtained using different weightings because they depend on the frequency distribution of the noise. For example, an amplifier with significant hum will have a lower noise weighting than an amplifier with evenly distributed noise. In most cases, however, Type A weighting should be expected to produce a noise level value 3 to 6 dB lower than unweighted.

Source impedance

Thermal noise is often the main source of noise in preamps and headphone amplifiers. And they are proportional to the impedance of the input circuit, which also includes the source. The higher the source impedance, the greater the noise. So, for example, a headphone amplifier will operate properly from a 100 ohm source, but using a 10k ohm source can easily result in audible noise. In this case, the noise you hear is actually coming from the input device, not the amplifier..

Noise measurement

Since the noise level value is the sum of the components in the range audio frequencies, and is also usually very low, measuring it accurately is very problematic. The best high-end PC hardware may have a fairly low noise floor, but at the same time rarely allows for measurements at maximum value at the output of the device. And, more importantly, PC audio hardware does not allow you to set the absolute value - in V, dBV, etc. Few digital multimeters have sufficient resolution and low enough noise floor to make measurements with µV accuracy in the range of 20-20000 Hz . Theoretically, it is possible to temporarily calibrate the 24-bit sound card using exact measuring device and corresponding test signals. But there are many nuances here, depending on the software used. Source impedance is also an issue. Developers prefer to short-circuit the input contacts of the device during measurements to obtain better noise indicators, however, closer to real results can be obtained by connecting a shunt resistance to the input that is close in value to the impedance of a typical source. If you try to use a real source, its noise will be included in the measurement result (as is the case with RMAA). When testing a DAC, it is necessary to use very low level signals, because if nothing is fed to the DAC at all, it will turn off completely and show incorrect results. Almost any quality audio analyzer will be able to eliminate this low-level signal from the results, leaving only noise.

Measurements with RMAA

Even if you were able to calibrate the levels, you still don't know what conversions are happening inside the RMAA program. It's a magical black box, with no credible documentation describing how the program calculates the output values. What frequency range was used? Is the result weighted or unweighted? Plus, the results include the unknown noise level of the equipment used. Eventually, the best way To measure noise is to use Audio Precision and Prism Sound analyzers.

Conclusion

Noises at –105 dBV (relative to 1 V) are almost always inaudible. Noise levels around -95 dBV are acceptable for most listeners. Noise levels specified in other units must first be converted to dBV or similar units before they can be compared. The results obtained using RMAA are usually uninformative because they cannot be used to determine absolute values. RMAA can only determine the dynamic range, and even then not always, since it is often difficult to adjust the levels correctly without special equipment.

Original article in English: Noise & Dynamic Range

What is noise, how to measure it, in what quantities. What is dynamic range and how does it differ from noise level?

Excessive noise is bad for more than just your hearing. According to WHO, about 2% of all deaths in the world are caused by diseases associated with excess noise.


Modern medicine considers loud sounds one of the formidable enemies of human health. In ecology, there is even the concept of “noise pollution”. In addition to hearing disorders, cardiovascular diseases and hypertension may occur. Metabolism, activity of the thyroid gland and brain are disrupted. Memory and performance decrease. Noise stress causes insomnia and loss of appetite. High noise levels can cause peptic ulcers, gastritis, and mental illness.

Noise through the conductive paths of the sound analyzer affects various centers of the brain, as a result of which the work is disrupted different systems body. According to the Austrian scientist Griffith, noise causes premature aging in 30 cases out of 100 and shortens the lives of people in large cities by 8-12 years. WHO experts consider a sound level of 85 dB safe for health, affecting a person daily for no more than 8 hours.

25-30 decibels

T What noise level is considered comfortable for a person. This is a natural sound background, without which life is impossible.

By the way…

In terms of volume, this is comparable to the rustling of leaves on trees - 5-10 dB, wind noise - 10-20 dB, whispering - 30-40 dB. And also with cooking on the stove - 35-42 dB, filling the bath - 36-58 dB, elevator movement - 34-42 dB, refrigerator noise - 42 dB, air conditioner - 45 dB.

The house should not be too quiet. When there is deathly silence around us, we subconsciously experience anxiety. The sound of rain, the rustling of leaves, the ringing of bells hanging in the doorway, the ticking of a clock have a calming effect on us and even have a healing effect.

We are used to thinking that silence is the absence of sounds, but, as it turned out, our brain clearly hears it and perceives it in the same way as other sounds. Scientists from Oregon State University in the USA found this out.

60-80 decibels

Such noise, which occurs regularly, causes disorders of the autonomic nervous system in a person and tires even with short-term exposure.

By the way…

Large store - 60 dB, washing machine- 68 dB, vacuum cleaner - 70 dB, playing the piano - 80 dB, baby crying - 78 dB, car - up to 80 dB.

The noise level is perceived subjectively, addiction is possible. But in relation to developing vegetative reactions, adaptation is not observed.

Constant traffic noise (65 dB) leads to hearing loss. Street noise disrupts the functioning of the hearing center in the brain and negatively affects behavior. This conclusion was reached by scientists from the University of California at San Francisco.

90-110 decibels

The sound is perceived as painful. Leads to hearing loss. With intense exposure to noise of 95 dB or higher, vitamin, carbohydrate, protein, cholesterol and water-salt metabolism may be disrupted. At a sound intensity of 110 dB, so-called “noise intoxication” occurs and aggression develops.

By the way…

Motorcycle, truck engine and Niagara Falls - 90 dB, redevelopment in an apartment - 90-100 dB, lawn mower - 100 dB, concert and disco - 110-120 dB.

According to GOSTs, production with such a noise level is harmful; workers must undergo regular medical examinations. People working in such conditions are 2 times more likely to suffer from hypertension. Workers in noisy professions are advised to take vitamins B and C.

If the player is turned on at full power, then the sound of about 110 dB affects the ears. There is a high risk of developing hearing loss (deafness).

115-120 decibels

This is the “pain threshold”, when the sound as such is practically no longer audible, pain is felt in the ears.

By the way…

The leaders in creating such noise are airports and train stations. The volume of a freight train when moving is more than 100 dB. When the train approaches the platform, the noise level on the platform is slightly less - 95 dB. Even a kilometer from the runway, the noise level from an airliner taking off or landing is more than 100 dB.

The noise level in the metro can reach 110 dB at stations and 80-90 dB in cars.

Don't get too carried away with karaoke. The level of acoustic load exceeds permissible limits, reaching 115 dB. After such extreme vocals, hearing is temporarily reduced by 8 dB.

140-150 decibels

The noise is almost unbearable, loss of consciousness is possible, and eardrums may burst.

By the way…

When starting jet engines of aircraft, the noise level ranges from 120 to 140 dB, the noise of a working drill is 140 dB, a rocket launch is 145 dB, a salvo of fireworks, a rock concert next to a huge powerful speaker, a car with a “broken” muffler is -120-150 dB .

180 decibels or more

Lethal to humans. Even metal begins to deteriorate.

By the way…

The shock wave from a supersonic aircraft is 160 dB, a shot from a 122 mm howitzer is 183 dB, the explosion of a powerful volcano is 180 dB.

According to research by American experts, the loudest sound in the animal kingdom is made by the blue whale - 189 dB.

Big city problems

According to experts, up to 70% of Moscow is subject to excess noise from various sources. The amount of excess reaches the following values:

  • 20-25 dB - near highways;
  • up to 30-35 dB - for apartments in houses facing major highways (without noise-proof glazing);
  • up to 10-20 dB - near railways;
  • up to 8-10 dB - in areas subject to periodic exposure to aircraft noise;
  • up to 30 dB - if the established requirements for conducting construction work at night are not met.

I can not hear

The human ear can only hear vibrations whose frequency ranges from 16 to 20,000 Hz. Oscillations with a frequency of up to 16 Hz are called infrasound, more than 20,000 Hz are called ultrasound, and the human ear does not perceive them. The highest sensitivity of the ear to sounds is in the frequency range 1000-4000 Hz. The higher the pitch of a sound or noise, the stronger its adverse effect on the organ of hearing. Infra- and ultrasound can be harmful to human health. However, the degree of their influence depends on the frequency and time of exposure.

Let me sleep!

Hearing sensitivity increases by 10-14 dB during sleep. According to WHO standards, cardiovascular diseases can occur if a person is constantly exposed to noise levels of 50 dB or higher at night. A noise level of 42 dB is enough to cause insomnia, and 35 dB is enough to simply become irritable.