An application example for duct noises as a basic model.
If any countermeasures have not been taken, the ventilation noise would go out into the neighboring high-rises. In such concrete fields, noises keep going without attenuation.
This picture shows the inside of the duct. The two speakers output control sounds to cancel low-frequency noises from the duct fan. Because of random signal noises, feedforward control is applied.
The photo shows Okayama university Hospital. It is an ANC application to
the construction site.
(Being constructed by Shimizu corporation)
The construction of an additional word is going on in the hospital premises, even though there are many hospitalized patients. So low-frequency noises must be treated.
Feedback control is used because the noise from the crane engine is periodic.
Video clip of the ANC result
The result shows the 100Hz periodic sound is suppressed by 20dB.
Caution) The relevant sound is 100Hz. Use a woofer speaker to play. Normal PC speakers or headphones can not reproduce the sound.
ANC is used to suppress exhaust gas noises from the machinery engines at a highway construction site.
This site is vast and open, but Low-frequency noises reach to the end of the site. The construction crews use ANC systems with consideration for the neighboring residents.
Feedback control is applied
ANC system is installed on the backhoe too.
ANC system is installed to cover silencers at diesel engine manufacturing plants.
The exhaust pipe for engines test bench has a silencer, but low-frequency sounds below 100Hz can not be attenuated. So ANC system is used with consideration for the neighboring residents.
The control speakers are moved closer to increase the ANC effect in case of a bigger power engine.
Tested engines got even more powerful. so more powerful speakers have been
The work was done in the blazing sun. (*_*);
ANC examples for several diesel engines on a pile driving ship.
ANC is applied for an exhaust gas outlet from the generator engine. The engine has a silencer, which can not suppress very low frequency noises under 100Hz.
Low-frequency sounds carry far on the sea and reach the shore.
The crew use ANC with consideration for residents around the bank protection work site.
The crew install the control speakers at the exhaust gas outlet of the
hydraulic pump for the pile driver.
The continuous engine low-frequency sound is more annoying than the pile hammering sounds.
(Photo of hydraulic pump from the above.)
This treatment of this ship is a perfect case.
The sound insulating boards are for high-frequency noises.
And for low-frequency noises....
Of cause, Active noise control system is involved. Those are the basics
for noise control.
(Photo of ANC speakers inside the sound insulating boards from the above.)
(Penta-ocean construction style)
The sound field near control speakers is linearly turbulent. In this method, it controls the near-field as if it controls far-field. (Kajima corporation style)
Sorry for no photos.
(Photos of sites using the virtual point control method are not allowed to be posted.)
ANC system used at the area requiring ear-plugs in a Tobacco-manufacturing plant
To protect the workers in front of the machine from damaging their ears.
They take good measures to contain noises inside, but some noises leak from apertures which are needed to operate lines.
The worker damage their health by low-frequency noises without putting ear-plugs.
ANC system suppresses harmonic sounds (60Hz fundamental) from the gears in the product line.
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KOBE, 651-1123, JAPAN
TEL +81-78-747-2722 (S.Awata)