Acoustic Resonator

Acoustic resonator

A device consisting of a combination of elements having mass and compliance whose acoustical reactances cancel at a given frequency. Resonators are often used as a means of eliminating an undesirable frequency component in an acoustical system. In other instances resonators are used to produce an increase in the sound pressure in an acoustic field at a particular frequency.

Resonators are useful most often in the control of low-frequency sound. They are of particular value in reducing the noise from sources having constant frequency excitation.

Resonators have also found considerable application in architectural acoustics. It is often difficult to obtain adequate control of reverberation time at low frequencies in a large studio or auditorium using conventional acoustical materials. A number of designs for these spaces have included the construction of resonators behind walls or in the ceiling to obtain increased low-frequency absorption and thus provide more satisfactory reverberation characteristics.

The Helmholtz resonator (see illustration) is the simplest and most often utilized acoustical resonator. The unit consists of a straight tube of length l and cross-sectional area S, connected to a closed volume V. This combination is directly analogous to the simple series LC electrical circuit. See Acoustic impedance

Helmholtz resonatorenlarge picture
Helmholtz resonator

Resonator, Acoustic


a vessel that is connected with the external medium through a small orifice or tube called the neck.

A characteristic feature of an acoustic resonator is the ability to execute low-frequency natural oscillations having a wavelength substantially greater than the resonator’s dimensions. The fundamental (natural) frequency f0 of an acoustic resonator with a neck is calculated from the formula f0Resonator, Acoustic, where c is the speed of sound in air, S and l are the cross-sectional area and length of the tube, respectively, and V is the volume of the vessel. If an acoustic resonator is placed in a harmonic sound field whose frequency is equal to f0, vibrations are produced in the resonator that have an amplitude many times the amplitude of the sound field. In a nonharmonic sound field, an acoustic resonator responds only to oscillations having a frequency equal to the natural frequency of the resonator. Consequently, a set of resonators having different natural frequencies can be used to analyze sound.

The amplitude of the oscillatory velocity in a resonator’s neck at f0 is high; consequently, when friction exists in the neck, a sound at this frequency is strongly absorbed. This property of an acoustic resonator is used to create acoustic resonance absorbers in architectural acoustics. Acoustic resonators are also used as resonance baffles to reduce the transmission of low-frequency noise along a sound duct. The low input impedance of an acoustic resonator in a sound duct wall at the frequency f0 will sharply alter the conditions for wave propagation at this frequency. Bubbles in a liquid and air cavities in certain other media, such as rubber, are also acoustic resonators, so that the presence of a large number of bubbles in water gives rise to strong sound absorption and interferes with the propagation of sound waves.

The theory of acoustic resonators was developed by H. Helmholtz and Lord Rayleigh.

acoustic resonator

[ə′küs·tik ′rez·ə‚nād·ər]
An enclosure that produces sound-wave resonance at a particular frequency.
References in periodicals archive ?
The new systems will join the other Endeavor AT tools already being used by the customer for high volume manufacturing of thin-film bulk acoustic resonator filters, which are an essential component in wireless communication systems, for example 4G/LTE smartphones, requiring advanced high-frequency RF filters.
The ACMD-7612 is an UMTS Duplexer manufactured with Avago's film bulk acoustic resonator (FBAR) technology which uses AlN piezoelectric material for resonating layers.
The MASCOT project's equipment uses an acoustic resonator on a sensor chip to check for a specific resonance frequency given off by gases, using a benchmark gas sample of less than one microlitre.
25-om GaAs enhancement-mode pHEMT process and leading-edge Film Bulk Acoustic Resonator (FBAR) filtering technologies, the module delivers superior performance across voltage and temperature levels.
Filtering Circuit with Coupled Acoustic Resonator 164
The new AFEM-S102 module integrates a Film Bulk Acoustic Resonator (FBAR) coexistence filter, SP3T antenna switch and TX path coupler in a small 2.
amp; SINGAPORE -- Avago Technologies (Nasdaq: AVGO), a leading supplier of analog interface components for communications, industrial and consumer applications, today announced two advanced Film Bulk Acoustic Resonator (FBAR) technology-based bandpass filters for next generation 4G WiMAX/LTE handsets, data cards and access points.
Avago's ACMD-7410/7609/7606 duplexers are low insertion loss, high isolation and high rejection duplexers that are achieved using Avago's proprietary Film Bulk Acoustic Resonator (FBAR) technology.
amp; SINGAPORE -- Avago Technologies (Nasdaq:AVGO), a leading supplier of analog interface components for communications, industrial and consumer applications, today introduced the industry's first highly integrated miniature GPS front-end modules that combine a film bulk acoustic resonator (FBAR) filter with a high-gain, low noise amplifier (LNA) that offers superior performance levels.
By integrating a GPS LNA with pre- and post high-rejection film bulk acoustic resonator (FBAR) filters, the high-performance ALM-1812 simplifies and shortens the RF design process, reduces component count and provides excellent RF performance levels that are critical in the use of GPS applications.
Infineon's bulk acoustic wave (BAW) business is a leader in high precision RF filtering for wireless applications and complements Avago's existing film bulk acoustic resonator (FBAR) filtering technologies.
The company's innovative enhancement-mode pHEMT, CoolPAM and Film Bulk Acoustic Resonator (FBAR) technologies have set new benchmarks for battery life, size and performance of mobile products.

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