Noise Level When Working with a Hammer
Sound volume. Noise level and its sources
The physical characteristic of sound volume is the sound pressure level, in decibels (dB). “Noise” is a random mix of sounds.
Sounds with low and high frequencies seem quieter than mid-range sounds of the same intensity. With this in mind, the uneven sensitivity of the human ear to sounds of different frequencies is modulated using a special electronic frequency filter, obtaining, as a result of normalization of measurements, the so-called equivalent (in energy, "suspended") sound level with dimension dBA (dB (A), that is. with a filter "A")
A person, in the daytime, can hear sounds with a volume of 10-15 dB and higher. The maximum frequency range for the human ear, on average, is from 20 to 20,000 Hz (possible range of values: from 12-24 to 18000-24000 hertz). In youth. midrange sound with a frequency of 3 KHz is better heard, in middle age. 2-3 KHz, in old age. 1 KHz. Such frequencies, in the first kilohertz (up to 1000-3000 Hz. the area of voice communication). are common in telephones and radio on the NE and DV bands. With age, the audible range decreases: for high-frequency sounds. decreasing to 18 kilohertz or less (in older people, every ten years. about 1000 Hz), and for low-frequency ones. increasing from 20 Hz or more.
In a sleeping person, ears become the main source of sensory information about the environment ("light sleep") Hearing sensitivity, at night and with eyes closed. increases by 10-14 dB (up to the first decibels, on the dBA scale), compared with the daytime, therefore, loud, sharp noise with large jumps in volume can wake sleeping people.
If there are no sound-absorbing materials on the walls of the premises (carpets, special coatings), the sound will be louder due to repeated reflection (reverberation, that is, an echo from the walls, ceiling and furniture), which will increase the noise level by several decibels.
Noise scale (sound levels, decibels), in the table
Maximum allowable sound pressure for the player’s headphones (according to European standards)
At sound levels above 160 decibels. possible rupture of the tympanic membranes and lungs,
more than 200. death (noise weapon)
The maximum allowable sound levels (LAmax, dBA). more "normal" 15 decibels. For example, for living rooms of apartments, permissible constant sound level in the daytime. 40 decibels, and the temporary maximum. 55. With constantly working engineering equipment. the amendment is taken into account. minus 5.
Inaudible noise. sounds not perceived by the ear, with frequencies less than 16-20 Hz (infrasound) and more than 20 KHz (ultrasound). Low-frequency oscillations of 5-10 hertz can cause resonance, vibration of internal organs and affect the functioning of the brain. Low-frequency acoustic vibrations increase aching pain in bones and joints in sick people. Infrasound sources: cars, wagons, thunder from lightning, etc.
In the workplace maximum permissible, according to the law, equivalent sound levels for intermittent noise: the maximum sound level should not exceed 110 dBA, but for pulsed noise. 125 dBAI. It is forbidden even a short stay in areas with deafening sound pressure levels. over 135 dB, in any octave band.
Cry baby, compared to other sounds of the same volume. much stronger effect on the human psyche, as an irritant and a stimulus to active physical actions (calm, feed, etc.)
In the construction of buildings and structures, in accordance with modern, more stringent requirements of sound insulation, technologies and materials capable of providing reliable protection against noise should be applied.
For fire alarm: the sound pressure level of the useful audio signal provided by the siren should be not less than 75 dBA at a distance of 3 m from the siren and not more than 120 dba at any point in the protected room (Section 3.14 of NPB 104-03).
High power siren and ship howler. presses more than 120-130 decibels.
Special Signals (sirens and "quack". Air Horn), installed on official vehicles, are regulated by GOST R 50574. 2002. The sound pressure level of the signaling device, when a special sound signal is supplied, at a distance of 2 meters along the horn axis, must not be lower than:
116 dB (A). when installing a sound emitter on the roof of a vehicle;
122 dBA. when installing the radiation in the engine compartment hood.
Changes in the fundamental frequency should be between 150 and 2000 Hz. Cycle time. from 0.5 to 6.0 s.
The horn of a civilian vehicle, in accordance with GOST R 41.28-99 and UNECE Regulation No. 28, must produce a continuous and monotonous sound with an acoustic pressure level. no more than 118 decibels. This order, the maximum permissible values. and for car alarms.
If a city dweller, accustomed to constant noise, finds himself, for some time, in complete silence (in a dry cave, for example, where the noise level is less than 20 db), then he may well experience depressive states, instead of rest.
The device a sound meter for measuring sound level, noise
To measure the noise level, a device is used sound level meter (in the photo), which is produced in different modifications: household (approximate price. 3-4 tr, measurement ranges: 30-130 dB, 31.5 Hz. 8 kHz, filters A and C), industrial (integrating and t.d.) Of the most common models, we can distinguish: SL, octave, svan. On the arrow indicators of noise meters. the arrow can, by inertia (with a certain dynamics of increasing sound level), fly away further than the peak value of the signal. Therefore, the final values (already processed by the chip, according to the algorithm of the selected filter) are removed from the digital display of the device.
For measurements of infrasound and ultrasonic noise. professional wide-range sound meters are used. If continuous monitoring is not required "acoustic smog", then are limited to single, estimated measurements. Devices are rented for a while, or a specialist with certified equipment is invited.
Sound frequency ranges
Sub-bands of the spectrum of sound frequencies, which are configured filters of two- or three-way speaker systems:
low-frequency. fluctuations up to 400 hertz;
mid-frequency. 400-5000 Hz;
high frequency. 5000-20000Hz
Musical classification, names of singing voices by frequency ranges, taking into account the gender of performers
Bass profundo (ultra-low, with a control). 44-262 hertz
Bass (low). 82-349 Hz
Baritone (medium). 110-392 Hz
Tenor (high). 132-532 Hz
Tenor Altino (Ultra High). 131-700 Hz
Contralto (low). 165-692 Hz
Mezzosoprano (medium). 220-880 Hz
Soprano (high). 262-1046 Hz
Coloratura soprano (the highest female voice, up to the note "F" third octave). 260-1400 Hz.
Frequency ranges of sounds produced when playing musical instruments:
Acoustic Guitar. 82-1175 hertz
Electric Guitar. 82-1570 Hz
Bass. 41-250 Hz
Pipe. 160-1200 Hz
Violin. 200-2800 Hz
Piano. 27-4200 Hz
Symphony Orchestra. 31-15000 Hz
Variety Orchestra. 25-16000 Hz
Brass Band. 50-10000 Hz
The speed of sound and its distribution range
The approximate speed of audible, mid-frequency sound (frequency of the order of 1-2 kHz) and the maximum range of its distribution in various environments:
in the air. 344.4 meters per second (at a temperature of 21.1 on the Celsius scale) and about 332 m / s. at zero degrees;
in water, approximately 1.5 kilometers per second;
in a tree of hard varieties. about 4-5 km / s along the fibers and one and a half times less. across.
At 20 ° C., The speed of sound in fresh water is 1484 m / s (at 17 °. 1430), in sea. 1490 m / s.
The speed of sound in metals and other solids (only the values of the fastest, longitudinal elastic waves are given):
in stainless steel. 5.8 kilometers per second.
Cast Iron. 4.5
Ice. 3-4km / s
Copper. 4.7 km / s
Aluminum. 6.3km / s
Polystyrene. 2.4 kilometers per second.
With increasing temperature and pressure, the speed of sound in air increases. In liquids, the inverse temperature dependence.
The propagation velocity of elastic longitudinal waves in rock masses, m / s:
dry / wet sand. 300-1000 / 700-1300
They reduce the range of sound propagation, along the surface of the earth. high barriers (mountains, buildings and structures), the opposite direction of the wind and its speed, as well as other factors (low atmospheric pressure, high temperature and low humidity). Distances at which the source of loud noise is almost inaudible. usually from 100 meters (in the presence of high obstacles or in a dense forest), up to 300-800 m. In open areas (with a fair average wind. the range increases to a kilometer or more). With distance "are lost" (faster quenched and scattered) higher frequencies and low-frequency sounds remain. The maximum distribution range of medium-intensity infrasound (a person does not hear it, but there is an effect on the body) is tens and hundreds of kilometers from the source.
The attenuation intensity (absorption coefficient) of medium-frequency sound (of the order of 1-8 kHz), at normal atmospheric pressure and temperature, above the ground with low grass, in the steppe is approximately 10-20 dB for every 100 meters. The absorption is proportional to the square of the frequency of the acoustic waves.
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If during a thunderstorm you saw a strong lightning and after 12 seconds you heard the first peals of thunder, it means that lightning struck four kilometers from you (340 12 = 4080 m). In approximate calculations, it is assumed. three seconds per kilometer of distance (in airspace ) to the sound source.
the line of propagation of sound waves deviates in the direction of decreasing the speed of sound (refraction by a temperature gradient), that is, on a sunny day, when the air at the surface of the earth is warmer than the overlying line, the line of propagation of sound waves bends upward, but if the upper atmosphere is warmer than the surface layer, then the sound will go back down from there and it will be better to hear.
Diffraction of sound. enveloping by waves of an obstacle when its dimensions are comparable to or less than the wavelength. If it is much longer than the wavelength, then the sound is reflected (the angle of reflection is equal to the angle of incidence), and an acoustic shadow zone is formed behind the obstacles.
Reflections of a sound wave, its refraction and diffraction. cause multiple echoes (reverberation), which has a significant impact on the audibility of speech and music indoors or outside, which is taken into account when recording, to produce live sound (by placing compact stereo images in optimally close areas microphones with a sharp directivity characteristic, for recording direct sound, followed by mixing and mixing of the “dry” recordings by the processor into a digit or using long-distance, equally remote, well tuned environment microphones with additional recording of reflected sounds).
Conventional sound insulation does not save from infrasound.
The Noisiest Cities
– these are many regional and district centers of the country, almost all the territories of large transport hubs and urban residential buildings along avenues and near airports. This category includes: Moscow, St. Petersburg, Krasnoyarsk, Rostov-on-Don, Chelyabinsk, Yekaterinburg, Perm, Irkutsk, Yaroslavl, Voronezh, Novokuznetsk, Nizhny Tagil, Magnitogorsk, Omsk, Ufa, Samara, Nizhny Novgorod, Novosibirsk, Murmansk , Perm, Tula, Ulyanovsk, Kemerovo and others.
The main sources of noise in the city are trams, cars, trucks, operating industrial enterprises and flying over low altitude, air liners. Even realtors adjust real estate prices, depending on the local level of noise load on a house with apartments for sale or for rent.
The trend is that the intensity of city noise, in connection with the increasing number of cars on the roads, is only growing. The general situation is aggravated by screaming, at low frequencies, car radios from cars and speakers from the open windows of high-rise buildings.
If, according to the decision of the municipal authorities, the flows of heavy vehicles are crowded out to long bypass roads, beyond the boundaries of settlements, and intra-city cargo transportation is allowed only at strictly certain hours of the day and only on streets permitted for this, the above measures will significantly improve the environmental situation and increase the comfort of living.
A separate story is the noise made by birds, insects, pets. This, for example, and barking dogs, and mewing cats. In household plots of private houses, there can be a lot of noisy animals. pigs screaming from hunger, screaming roosters, loudly gaggling geese, mooing cows. Therefore, the private sector on the outskirts of cities often resembles a large village, according to the characteristic sounds of the rural discord.
Noise from air conditioners and refrigerators
Modern split air conditioning systems operating in quiet mode (designed specifically for nighttime use) usually do not exceed the sound level acceptable by standards for residential premises. But this condition is only feasible only for indoor (indoor) units of the air conditioner. External (street, window) units with a compressor and exhaust fan, located outside the premises. make a lot more noise and, as they say, "all the way". In the instruction, on external blocks, decibel values are indicated, but these are significant values. For the nearest neighbors, whose windows face the same side of the wall of a multi-storey building, this is a real problem causing inconvenience.
Malfunctions in the operation of the refrigerator motor (violation of the rotor alignment, poor assembly and defective components) can cause strong vibration and excessive noise. If, in addition, there are no damping rubber gaskets under the legs, then the vibration is transmitted to the floor and further to the floor slab.
Loud sound and ultrasound with a frequency of 20-50 kilohertz, reproduced with a modulation of several hertz. are used to scare away birds from airfields, animals (dogs, carnivores) and insects (mosquitoes, midges), if only they are not deaf. Infrasonic repellents (at a frequency that causes an uncontrolled sense of fear and panic state), of sufficient power. can act, even at the level of the internal organs of a living organism, causing their resonance to vibrations. The most compact and wide-range emitters include piezo sound emitters.
The toxicity of sound depends on the shape of the signal, which has a stepwise (for example, rectangular) or smooth (for example, sinusoidal) graph, and on the phase difference of the oscillations when they are mixed. Ready-made sound files and tuning presets can be found and downloaded on the Internet.
Acoustic scarecrows and noise-shockers are not an absolutely reliable means of protection, since the degree of their impact depends on many factors. individual characteristics, directivity and power of the emitter, working conditions, etc. In professional equipment, standard means of combined action are used. For example, if it is necessary to completely clean the protected area from moles, mice and rats, not only acoustic but also seismic emitters (periodically transmitting mechanical vibrations to the ground) are used.
When working with equipment, the safety precautions specified in the instructions for each device should be observed and not to violate safety rules.
After the aircraft overcomes the speed of sound (Mach = 1), the moment of passing the front of the Mach cone is accompanied by a sharp, like explosion, loud bang. Overcoming each subsequent sound barrier (M = 2,3,4. Mach numbers). narrows the cone of the shock wave (shock wave) and makes "boom" even louder.
The observer hears a roar when a very rapidly moving body (plane, projectile or bullet) has already passed by. For example, when shooting with a Mosin rifle, with a standard cartridge, at a kilometer distance. the sound of a shot comes out approximately two seconds after the bullet arrives and hits the conditional target. At subsonic speeds, on the contrary. first the noise approaches (rustling, whistling, howling of a mine or shell), and then. its source.
Hypersound. moving faster than 5 Machs.
At the exit of mines or shells fired at maximum range, along a flat ballistic trajectory. their speed, usually already subsonic.
Binaural Beat Frequency
When the right and left ears hear sounds (for example, from the player’s headphones, f 20-30 hertz), the sounds decay, in perception, into the source ones with their actual frequency, and the bin effect disappears. The phase difference of the sound waves coming to the right and left ear. allows you to determine the direction of the sound / noise source, its volume and timbre. the distance to it.
International standardization of physical parameters
Since the beginning of the 20th century, the International Electrotechnical Commission (IEC, the organization’s website is located at https://www.iec.ch/) has contributed to the development and dissemination of standards. The Russian Federal Agency for Technical Regulation (Rosstandart) is a full member of this organization. The International Electrotechnical Vocabulary (IEV) has been published by the IEC in order to combine electrical terminology. There are several domestic Internet resources from which you can, in whole or in part, download this document in translation into Russian.
The national standards of IEC member countries are identical or modified with respect to international ISO standards. As an example "GOST R 52797.1-2007 Acoustics. Recommended design methods for low-noise workplaces of production facilities. Part 1. Principles of noise protection" and other regulatory documents.
Information in the universal Internet encyclopedia:
https: // ru.wikipedia.org/wiki/Sound Volume
In those places of the ionosphere where electromagnetic waves of sufficient power beat, when Schumann resonance is established (with a high quality factor), especially at the frequencies of its first harmonics, the resulting plasma bunches begin to emit infrasonic acoustic (sound) waves. Specific ionospheric emitters exist until lightning discharges continue in the initiating thunderstorm source. up to about the first tens of minutes. For an eight-MHz frequency, these emitting points are located on the opposite side of the globe, from an electromagnet source. waves. On the 14th hertz. along the triangle. Local, highly ionized regions in the lower layers of the ionosphere (sporadic layer Es) and plasma reflectors can be interconnected or spatially coincide.
How to keep your hearing
Long-term exposure to noise levels above 80-90 decibels can lead to partial or complete hearing loss (at concerts, the power of speakers can reach tens of kilowatts). Also, pathological changes in the cardiovascular and nervous system can occur. Absolutely safe for the human ear. only sounds with a volume of up to 35 dB.
The response to a long and loud noise exposure is tinnitus. ringing in the ears, "noise in the head", which can develop into a progressive hearing loss. Characteristic for ages over 30 years, with a weakened body, stress, abuse of AL-KOgol and smoking. In the simplest case, the cause of ear noise or hearing loss may be the sulfur plug in the ear, which can be easily removed by a specialist (washing or removing). If the auditory nerve is inflamed. it can be cured, it is also relatively simple (with medicines, acupuncture). Pulsating noise is a more difficult case for treatment (possible causes: narrowing of blood vessels in atherosclerosis or tumors, as well as subluxation of the cervical vertebrae).
To protect your hearing:
Do not increase the sound volume in the player’s headphones, trying to drown out external noise (in the subway or on the street). This increases the electromagnetic radiation to the brain from the earpiece speaker;
in a noisy place, to protect your hearing. use anti-noise soft "ear plugs", earbuds or headphones (noise reduction is more effective at high frequencies of sound). They must be individually customized under the ear. In the field, they also use bulbs from a flashlight (they are not for everyone, but they fit in size). In shooting sports, individually cast "active ear plugs" with electronic filling, for the price. like a phone. They must be stored in packaging. It is better to choose bershee made of a hypoallergenic polymer, having good SNR (noise reduction), at a level of 30 dB or more. In case of sharp pressure drops (in an airplane), for its equalization and reduction of pain. it is necessary to use special vents with micro-holes;
indoor use soundproofing eco-friendly materials to reduce noise;
when underwater immersion, so that the eardrum does not rupture. to be purged on time (to purge the ears with your nose or swallowed). Immediately after diving. not on a plane. Jumping with a parachute. you also need to timely equalize the pressure so as not to get a barotrauma. The consequences of barotrauma: noise and ringing in the ears (subjective tinnitus), hearing loss, earache, nausea and dizziness, in severe cases. loss of consciousness.
with a cold and a runny nose, when the nose and maxillary sinuses are stuffed up, sudden drops in pressure are unacceptable: diving (hydrostatic pressure. 1 atmosphere per 10 meters of immersion depth in water, that is: two. at ten, three. at around 20 m. and etc.), parachute jumps (0.01 atm. per 100 m. height, increases rapidly, with acceleration).
// approximately seven and a half millimeters of mercury of the barometer. for every hundred meters, in height.
give your ears a break from loud noise.
Techniques used, usually, to balance the pressure on both sides of the eardrum: swallowing, yawning, purging with a closed nose. The Frenzel method. holding the nostrils, with an effort to pull the tongue back, on the palate (with muscle contraction, the nasal cavities and Eustachian tubes open). Gunners, firing a shot. open their mouths or cover their ears with the palms of their hands.
Common causes of hearing loss: ingestion of water, infection (including respiratory organs), trauma and swelling, the formation of sulfuric cork and its swelling upon contact with water, prolonged exposure to noisy conditions, barotrauma with a sharp pressure drop, inflammation of the middle ear. otitis media (congestion fluid behind the eardrum).