New sound-absorbing material. Scheme, description

Free technical library

ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
Free library / Schemes of radio-electronic and electrical devices

The new sound-absorbing material makes it possible to reduce the sound pressure inside the speaker by 50 times (!) Encyclopedia of radio electronics and electrical engineering

Free technical library

Encyclopedia of radio electronics and electrical engineering / Speakers

Comments on the article

One of the main problems of sound reproduction is the sound quality, the effective functioning of sound sources. In this technique, contradictions have accumulated between the possibility of recording and reproducing electrical signals of the audio range with high reliability, on the one hand, and the low quality of converting electrical signals into sound signals, on the other hand. With the advent of digital recording of electrical signals, all questions regarding the quality of recording and playback have been practically removed, however, the significant use of these achievements is difficult due to insoluble problems that occur in the reproduction of low frequencies and spurious harmonics, primarily due to the pneumatic reaction of the volume of sound speakers, especially in inexpensive and small-sized ones.

Suffice it to say that when reproducing low frequencies, even in 100-liter speakers, the cone of the low-frequency head experiences loads due to the pneumatic effect up to 3:4 kg.s. This pneumatic force limits the range of oscillations of the diffuser, and also causes its spontaneous deformation and numerous resonances, both in the diffuser itself and in the volume of the column. Limiting the range of oscillations causes a decrease in the amplitude-frequency characteristic at low frequencies, and spurious resonances - a harmonic distortion of the reproduced signals.

The decline in the amplitude-frequency characteristic in 100-liter speakers starts at about 60 Hz, to ensure high-quality sound from 30 Hz, the speaker volume is already 400 liters.

As you can see, even in very expensive speakers, up to 400 liters, a whole octave is unsatisfactorily reproduced - 16:32 Hz, and harmonic distortion is 20 times higher than the permissible values. In columns of average cost, with a volume of 60:100 liters, the second octave is unsatisfactorily reproduced - 32:64 Hz and the first is practically absent, while harmonic distortion exceeds the allowable limit by 50:100 times.

The last word in solving this problem is an active subwoofer - a separate loudspeaker designed to reproduce exclusively the low-frequency region of the sound spectrum. The dimensions of such subwoofers range from 70:40 liters, the frequency range, as a rule, is 30:150 Hz, but the "sweet-voiced" speakers do not exceed 10:12 liters. The rise of low frequencies in subwoofers is provided by forced amplification modes built into it by an amplifier, which inevitably generates an increase in harmonic distortion. To match a subwoofer to a pair of standard speakers, a special digital filter is required - all together leads to a price of about 500 US dollars.

As you can see, improving the acoustic characteristics of small-sized speakers with the help of sound absorption inside the box is still attractive.

The proposed new original technical solution for the formation of a sound-absorbing environment can significantly simplify the situation. The decrease in sound pressure in such an environment up to 50 times has been experimentally obtained. In addition, the sound-absorbing medium, compared to air, has a significantly higher viscosity, this quality, combined with the ability to reduce sound pressure, has the most favorable effect on the suppression of numerous resonances in the box, i.e. leads to smoothing (straightening) of the amplitude-frequency characteristic and a decrease in harmonic distortion. There are no restrictions on the dimensions and shape of the absorbing medium, on the magnitude of the sound pressure.

A modern acoustic system contains, as a rule, 3 electro-acoustic transducers: high-frequency, mid-frequency and low-frequency (woofer). The first 2 transducers do not require large volumes for high-quality sound reproduction, therefore they are supplied already packaged, and the woofer requires large volumes, so its housing is the speaker cabinet. The new technical solution will reduce the physical dimensions of the woofer cabinet to the dimensions of the woofer itself and opens up the possibility of supplying it also in a cabinet, then special requirements for the speaker cabinet disappear.

For example, enclosing a 10" woofer with 6 liters of damping media provides the following performance:

Frequency range (with unevenness of 0,5 dB and a decline of 31,5 Hz-6 dB) - 31,5 ... 1250 Hz.
The maximum acoustic pressure is 110 dB.
Harmonic coefficient at 90 dB - 0,5%

Table 1. LIMITS AND CURRENT AUDIO ACCURACY.
Main parameters.	Numerical recording and reproduction of electrical signals in the audio range.	The limits of man.	World-class electro-acoustic transducers (output speakers) MONOLITH-111X	Domestic speakers 35-AC (running for music lovers)	Top domestic speakers 3 SL-113
Frequency reproduction band, Hz.	10-20000	16-22000	28-24000	50-20000	63-25000
Frequency response unevenness, dB.	0.5	0.5	⁺/_-2	⁺/_-5	⁺/_-3
Nonlinear distortion (clear factor), %.	0.005	0.05	1	12	2
Dynamic range, dB.	90	120	120	100	110
Preferred loudness (dynamic range), dB.	-	80 for amateurs. 90 for professionals	-	-	-
Volume, liters.	-	-	380	70	125
Cost, USD.	500	-	7000 for a couple	300 for a couple	500 for a couple

New sound-absorbing material allows 50 times (!) to reduce the sound pressure that occurs inside the speaker
Fig. 1

New sound-absorbing material allows 50 times (!) to reduce the sound pressure that occurs inside the speaker
Fig. 2

Compared to a modern subwoofer, the reproduction of low frequencies with the help of the proposed solution is half an octave deeper even with acoustic design of a closed type, the cone experiences a pneumatic load no more than in free space, the medium is viscous, as evidenced by the disappearance of the self-resonance of the speaker system - all this ensures extremely low harmonic distortion. If we take into account that the new technical solution provides an order of magnitude smaller dimensions, does not need an amplifier and an expensive digital filter, and provides a price several times lower, then you involuntarily begin to solidify with those who believe that modern subwoofers are a "step aside" : "a gesture of desperation born of the realization of the serious limitations in achieving the deepest basses with classical loudspeakers." The real way to solve the problem of deep bass opens Russian patent No. 2107949 for the invention "Device for high-quality sound reproduction".

Author: Doctor of Sciences I. Vozhenin; Publication: compnet.ru/nika

See other articles Section Speakers.

Read and write useful comments on this article.

<< Back

Latest news of science and technology, new electronics:

Artificial leather for touch emulation 15.04.2024

In a modern technology world where distance is becoming increasingly commonplace, maintaining connection and a sense of closeness is important. Recent developments in artificial skin by German scientists from Saarland University represent a new era in virtual interactions. German researchers from Saarland University have developed ultra-thin films that can transmit the sensation of touch over a distance. This cutting-edge technology provides new opportunities for virtual communication, especially for those who find themselves far from their loved ones. The ultra-thin films developed by the researchers, just 50 micrometers thick, can be integrated into textiles and worn like a second skin. These films act as sensors that recognize tactile signals from mom or dad, and as actuators that transmit these movements to the baby. Parents' touch to the fabric activates sensors that react to pressure and deform the ultra-thin film. This ... >>

Petgugu Global cat litter 15.04.2024

Taking care of pets can often be a challenge, especially when it comes to keeping your home clean. A new interesting solution from the Petgugu Global startup has been presented, which will make life easier for cat owners and help them keep their home perfectly clean and tidy. Startup Petgugu Global has unveiled a unique cat toilet that can automatically flush feces, keeping your home clean and fresh. This innovative device is equipped with various smart sensors that monitor your pet's toilet activity and activate to automatically clean after use. The device connects to the sewer system and ensures efficient waste removal without the need for intervention from the owner. Additionally, the toilet has a large flushable storage capacity, making it ideal for multi-cat households. The Petgugu cat litter bowl is designed for use with water-soluble litters and offers a range of additional ... >>

The attractiveness of caring men 14.04.2024

The stereotype that women prefer "bad boys" has long been widespread. However, recent research conducted by British scientists from Monash University offers a new perspective on this issue. They looked at how women responded to men's emotional responsibility and willingness to help others. The study's findings could change our understanding of what makes men attractive to women. A study conducted by scientists from Monash University leads to new findings about men's attractiveness to women. In the experiment, women were shown photographs of men with brief stories about their behavior in various situations, including their reaction to an encounter with a homeless person. Some of the men ignored the homeless man, while others helped him, such as buying him food. A study found that men who showed empathy and kindness were more attractive to women compared to men who showed empathy and kindness. ... >>

Random news from the Archive

Electric car as a backup power source in the house 09.03.2022

American General Motors Co. launches a pilot project where the company's electric vehicles can be used as backup power sources in customers' homes.

The project will be implemented jointly with Pacific Gas and Electric Company, the key operating company of the California generating PG&E Corporation.

The first tests are planned to be carried out closer to the summer, larger ones - by the end of this year. It is assumed that electricity from a charged electric car will be transferred to the house automatically using special software and data transfer protocols.

PG&E CEO Patty Poppy said that the ability to use electric vehicles as a backup power source will be a significant advantage, as well as help in the fight against climate change.

A similar project is currently underway by Ford Motor and Sunrun Inc. The latter is one of the leaders in the US solar energy market.

The launch of the experiment is scheduled for this spring.

Other interesting news:

▪ ATA6026 Highly Integrated Motor Driver

▪ Billions of tons of diamonds discovered in the bowels of the Earth

▪ A painted window becomes a solar panel

▪ Ultrabook hybrid Toshiba Portege Z10T

▪ Treatment of herpes with infrared light

News feed of science and technology, new electronics

Interesting materials of the Free Technical Library:

▪ section of the website Basics of First Medical Aid (BFA). Selection of articles

▪ article All this jazz. Popular expression

▪ article Which Japanese managed to survive two atomic bombings in a row? Detailed answer

▪ Lima article. Legends, cultivation, methods of application

▪ article Biofuel combustion plants. Boilers for burning sludge. Encyclopedia of radio electronics and electrical engineering

▪ article Antenna orientation device. Encyclopedia of radio electronics and electrical engineering

Leave your comment on this article:

Comments on the article:

Jury
[down] Reduces the pressure inside the column by 50 times, but what kind of material from the article is not clear. Two links: one to the same article, I another how to reduce noise in the car. The use of a sound-absorbing medium inside acoustics has been known for decades, but there is no sound in such acoustics. Musical instruments sound like boots.

All languages of this page

Home page | Library | Articles | Website map | Site Reviews