Toyota in 2008 introduced an interesting, though not new, development - an active noise reduction system that allowed to significantly reduce the noise level in the car. The system did not receive much popularity at the time of release, but over time, everything changes, and it is likely that it will become one of the most popular technologies.
Purpose of the car system
During operation, the car produces a lot of extraneous noise of varying intensity from various mechanisms - the chassis, engine, transmission and body elements. The search for ways to eliminate noise has been carried out for a long time and is very successful: modern cars are almost silent. Despite this, in the car's interior when driving at high speed, external noise remains, causing discomfort to passengers and the driver.
Toyota proposed its own way to eliminate this problem in 2008, introducing an active noise reduction system in cars. The technology itself was by no means new, but it was first used in the automotive industry, where it showed its effectiveness.
Modern noise reduction systems reduce the overall noise level by 5-8 dB, working mainly with low-frequency sound vibrations, which form the noise curtain in the cabin. Many automakers are developing such systems, which makes it possible to equip most modern cars with them.
The operation of the noise reduction system in theory
The fight against noise was traditionally conducted by passive means - either the source of noise, or the place that should be protected from sounds, got off with sound-absorbing and sound-reflecting materials, which are considered a passive noise reduction system. The active system is more effective - for example, automobile silencers that use the properties of sound waves. Eliminate third-party sounds can also be done electronically.
Sound is a wave consisting of alternating areas with reduced and increased pressure, moving at a speed of 330 m / s. Like any other wave, sound waves can undergo diffraction, interference, that is, interact with each other. The interference in the field of active noise reduction is of the greatest interest.
Interference can provoke unexpected and rather interesting results. For example, two sound waves of the same frequency encountered at the same point in space and phase mutually reinforce each other, respectively, the overall volume at this point will be sharply increased. Most often, owners of stereo systems or audio systems with a subwoofer encounter this phenomenon - in the room where they are installed, there are several areas in which the bass becomes deeper and more powerful. A similar effect is explained by the superposition of low-frequency sounds in the phase at a specific point on each other, which provokes their amplification.
There is also the opposite effect that occurs in the case of superposition of waves in antiphase: high-pressure regions overlap with low-pressure regions, which completely dampens the wave. However, in practice it is impossible to completely suppress the waves, but the overall sound intensity can still be reduced. Actually, active noise reduction systems are based on this phenomenon.
For the first time, such systems were implemented in headphones designed for builders, industrial workers and other organizations, after which the technology began to be used in headphones for listening to music, cars and homes. The principle of operation of the noise reduction system is quite simple: microphones are installed on the outside of the headphones that pick up third-party sounds. The built-in electronic unit changes the phase of the sounds coming from the microphones, so that they can be reproduced by the speakers. Accordingly, sounds from speakers and external sounds are supplied to the eardrum, and since they are in antiphase, they are suppressed.
Similarly, noise reduction systems in cars work.
Device car noise canceling system
The device of automobile noise reduction systems includes the following elements:
- System of microphones built into the ceiling of the cabin;
- A system of speakers located at different points in the cabin. The most commonly used audio system;
- Sensors located on the engine, suspension and other components of the car, which are the main sources of sound:
- Electronic control unit.
How does the active noise canceling system work in cars?
The electronic unit of the system receives information about extraneous noise from sensors and microphones. Based on the data obtained, phase changes are made to the incoming sounds, which are reproduced by the speakers and, when faced with noise in antiphase, reduce their intensity. As a result, a space is formed in the cabin in which the noise level from the engine, wheels and other mechanisms is significantly reduced.
A self -made active noise reduction system in a car does not do without sensors, since they capture noise that occurs when the suspension and wheels hit, and other sharp sounds. The classical system of speakers and microphones only captures sounds that are constant in intensity and constant - an even hum of the engine, body vibrations or the rustling of wheels on the road surface. The system is not able to respond to a sharp change in sounds, skipping loud noises - crashing, clanking and others.
Sensors are used to track sudden changes in the background sound. The electronic unit, based on the data received from the sensors, makes changes to the sound picture formed by the speakers, due to which a more effective suppression of external noise is achieved.
It is worth noting that the noise level produced by cars equipped with active noise reduction systems remains unchanged, since the system does not eliminate it, but creates a space in the cabin with a reduced level of external noise. Such technologies make the trip more comfortable, but do not eliminate the need for soundproofing of individual vehicle components.
Noise reduction system for home
Providing complete silence in an apartment or private house located in the city is quite difficult. This problem can be partially solved by installing double-glazed windows, but they do not guarantee complete silence. However, science and technology do not stand still, and many engineers are trying to solve this problem by creating active noise cancellation systems with their own hands.
Austrian Rudolph Stefanich created one of the most effective noise reduction devices Sono. Compact and simple system designed to eliminate unpleasant and annoying sounds and keep pleasant.
The principle of operation of the active noise reduction system in the Sono apartment is based on the operation of sensors and microphones that detect third-party noises and filter them by reproducing similar sounds in antiphase.
Acoustic music headphones work in a similar way.
Sono system device
The design of the Sono device is quite interesting and is presented by a speaker, a microphone with vibration sensors and a microprocessor. The device is made in the form of a small compact disk and is placed on the window pane using special suction cups. Sono uses window glass as a resonator.
Fixing and elimination of extraneous sounds is carried out in accordance with the settings. In the premises of the apartment, already processed noises are reproduced through the built-in speakers.
Sono's batteries are batteries that can be recharged from ambient electromagnetic radiation, such as Wi-Fi networks.
Sono device functionality
The capabilities of the active noise reduction system for the home allow you to filter annoying third-party noises, reproducing through the speakers only pleasant sounds. The user can make the appropriate settings in the device menu.
An additional and no less useful feature is the ability to play soothing and pleasant to hear sounds - rustling of the forest, surf noise and the like.
Where to buy the Sono system?
Unfortunately, there is no Sono active noise canceling system for sale today: despite the fact that the device reached the final of the James Dyson competition, it exists only as a prototype and requires investment. It is not yet known exactly whether it will be on sale or not. The author of the device is in an active search for investors and partners who can help launch the device in mass production.
Active Sound System
Active sound design systems are used to give the exhaust system the desired tone. The design is similar to an active noise reduction system: microphones, audio system, speakers and control unit. The only difference is that an altered sound is formed at the output of the audio system, not an antiphase.
The buttons located on the dashboard allow you to change the sound character of the exhaust system. Despite the fact that such systems are complex from a technological point of view, there is no particular practical benefit from them - they are mainly installed to satisfy the driver’s wishes of the owner. It should be noted that the changed active sound is heard only in the passenger compartment.