In 2008, Toyota introduced an interesting, though not new, development - an active noise reduction system, which made it possible to significantly reduce the noise level in the car. The system was not particularly popular at the time of release, but over time everything changes, and it is likely that it will become one of the most sought-after technologies.
Purpose of the car system
During operation, the car produces a lot of third-party noise of varying intensity from various mechanisms - chassis, engine, transmission and body elements. The search for ways to eliminate noise has been going on for a long time and very successfully: modern machines are almost silent. Despite this, when driving at high speed, third-party noise persists in the passenger compartment, causing discomfort to passengers and the driver.
Own way to eliminateThis problem was proposed in 2008 by Toyota, introducing an active noise reduction system in a car. The technology itself was by no means new, but it was first used in the automotive industry, where it proved to be effective.
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 allows them to be equipped with most modern cars.
The operation of the noise reduction system in theory
Noise control has traditionally been done by passive means - either the source of the 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. An active system is more efficient - for example, car mufflers that use the properties of sound waves in their work. You can also eliminate third-party sounds with the help of electronics.
Sound is a wave consisting of alternating areas of low and high pressure, moving at a speed of 330 m/sec. Like any other waves, sound waves can be subject to diffraction, interference, that is, to interact with each other. The interference for the ANC study area is of most interest.
Interference can provoke unexpected and rather interesting results. For example, meeting at the same pointspace and phase, two sound waves of the same frequency mutually reinforce each other, respectively, the overall volume at a given point will be sharply increased. Most often this phenomenon is experienced by owners of stereo systems or audio systems with a subwoofer - 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 phase at a specific point on top of each other, which provokes their amplification.
There is also an opposite effect that occurs when waves are superimposed in antiphase: high pressure areas are superimposed on low pressure areas, which completely dampens the wave. However, in practice, complete suppression of waves cannot be achieved, but the overall sound intensity can still be reduced. Actually, active noise cancellation systems are based on this phenomenon.
These systems were first implemented in headphones intended for builders, industrial workers and other organizations, after which the technology began to be applied to 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 outer side of the headphones that pick up third-party sounds. The built-in electronics block changes the phase of the sounds coming from the microphones, so that they can be reproduced by the speakers. Accordingly, sounds from the speakers and external sounds are supplied to the eardrum, and since they are located inantiphase, then they are extinguished.
Noise reduction systems in cars work in a similar way.
Automotive noise reduction device
The car noise reduction device includes the following items:
- In-ceiling microphone system;
- The system of speakers located at different points in the cabin. The most commonly used audio system;
- Sensors located on the engine, suspension and other vehicle components that are the main sources of sound:
- Electronic control unit.
How Active Noise Cancellation works in cars
The electronic unit of the system receives information about third-party 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, encountering noises 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.
Do-it-yourself active noise reduction system in a car is indispensable without sensors, because they fix the noise that occurs when the suspension and wheels hit, and other harsh sounds. The classic system of speaker and microphones captures only constant and constant sounds - the smooth hum of the engine, vibrations of the body or the rustling of wheels on the road surface. The system is notis able to respond to a sharp change in sounds, passing loud noises - roar, clang and others.
Sensors are used to track abrupt changes in the sound background. The electronic unit, based on the data received from the sensors, makes changes to the sound picture formed by the speakers, due to which more effective suppression of third-party noise is achieved.
It is worth noting that the noise level produced by vehicles 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 outside noise. These technologies make driving more comfortable, but do not eliminate the need for soundproofing of individual vehicle components.
Home Noise Reduction System
It is quite difficult to ensure complete silence in an apartment or a private house located within the city. This problem can be partly 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 reduction systems with their own hands.
Austrian Rudolf Stefanich created one of Sono's most effective noise canceling devices. The compact and simple system is designed to eliminate unpleasant and annoying sounds and keep pleasant ones.
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 noise and filter themby reproducing similar sounds in antiphase.
Acoustic music headphones function in a similar way.
Sono system device
The design of the Sono device is quite interesting and is represented by a speaker, a microphone with vibration sensors and a microprocessor. The device is made in the form of a small compact disc and is placed on the window glass with the help of special suction cups. Sono uses window glass as a resonator.
Fixation and elimination of extraneous sounds is carried out in accordance with the established settings. Already processed noises are reproduced through the built-in speakers in the premises of the apartment.
Sono's batteries are batteries that can be recharged by ambient electromagnetic radiation such as Wi-Fi networks.
Sono device functionality
Active Noise Canceling features for the home filter out annoying outside noise, reproducing only pleasant sounds through the speakers. The user can make the corresponding settings in the instrument menu.
An additional and no less useful feature is the ability to play soothing and pleasant sounds - the rustles of the forest, the sound of the surf and the like.
Where to buy a Sono system?
Unfortunately, there is no Sono active noise reduction system on the market today: despite the fact thatthe device reached the finals of the James Dyson competition, it exists only in the form of a prototype and requires investment. It is not yet known for sure whether it will be on sale or not. The author of the device is actively looking for investors and partners who can help launch the device into mass production.
Active Sound System
Active sound design systems are used to give the exhaust system the desired tone of performance. The design is similar to the active noise reduction system: microphones, audio system, speakers and control unit. The only difference is that the output of the audio system is a modified sound, and not anti-phase.
The buttons located on the dashboard allow you to change the character of the sound 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 modified active sound is heard only in the car.
