269 results about "Acoustic attenuation" patented technology

A silencer for a CPAP device comprises a housing assembly defining a flow path passing therethrough and including at least one of an inlet chamber, an acoustic chamber and a blower chamber. Each of the chambers has an inlet and an outlet for fluid communication therebetween. The silencer includes a combination of reactive components, resonators and dissipative elements disposed within the inlet, acoustic and blower chambers. The reactive component may be configured as a compliant-walled reactive tube. The resonator may be configured as a perforated plate defining a cavity volume. The dissipative element may comprise porous material substantially occupying the cavity volume bounded by the perforated plate in the chamber walls.

A pump piston assembly has a pump cylinder, at least one hollow piston slidably mounted for reciprocating motion in the pump cylinder, the piston having an inner surface of a first diameter and an outer surface of a second diameter, and a liner sleeve of a different material from the piston mounted on the inner or outer surface of the piston with a close or friction fit to the diameter of the piston surface on which it is mounted. The liner sleeve is of an acoustic dampening material which has a lower acoustic frequency than the piston material and is configured to absorb harmonic acoustic vibrations resulting from reciprocation of the piston in the cylinder.

A gas turbine engine comprising a fan section, a compressor, a combustor and a turbine, includes a nacelle having an inner nacelle surface defining an inlet duct designed to reduce an inlet duct area of the inlet duct to increase acoustic attenuation. The gas turbine engine also includes a spinner, disposed forward of the fan section, that includes features to increase acoustic attenuation. In one embodiment of the present invention, the nacelle includes a nacelle contoured surface protruding radially inward from the inner nacelle surface to reduce the inlet duct area. In a further embodiment of the present invention, the spinner includes a spinner contoured surface for reducing the inlet duct area. In other embodiments, the nacelle and/or the spinner include an inflatable bladder, a SMA actuator, a fluidic actuator, or a combination thereof, selectively activated to increase acoustic attenuation during certain conditions of an aircraft.

Acoustic attenuation materials are described that comprise outer layers of a stiff material sandwiching a relatively soft elastic material therebetween, with means such as spheres, discs or wire mesh being provided within the elastic material for generating local mechanical resonances that function to absorb sound energy at tunable wavelengths.

This acoustic attenuation panel for an aircraft engine nacelle comprises a structuring skin (1) and, by way of acoustic absorption material, a porous material (5) attached to this skin (1).

An internal duct of an aircraft engine pod may include a fan and a tubular air intake having a first acoustic attenuation internal tubular piece. The first acoustic attenuation internal tubular piece is acoustically homogeneous, is of the resonator type, and has no internal assembly fish-plate. Additionally, the internal duct may include a tubular fan casing and a tubular transition part for connecting the air intake to the fan casing. An internal face of the tubular transition part is acoustically homogeneous also. Moreover, the internal face of the first acoustic attenuation internal tubular piece and the internal face of the tubular transition part are disposed in aerodynamic continuity.

The measuring device comprises a computer used for data process, a signal process circuit connected to the computer, a pulse wave transmitting/receiving circuit connected to the signal processing circuit; a bandwidth transmitting/receiving transducer assembly connected to the pulse transmitting/receiving circuit. The data process program compares the measuring signal with the preset standard substance; the actually measured acoustic attenuation spectrum is combined with the acoustic attenuation spectrum obtained based on the scattering formula computational theory to construct the matrix and linear equation; using dual frequency attenuation ratioing to realize the calculation of average particle size; according to the particle size, inversely computes the particle concentration.

An auscultation system includes a transducer for generating an acoustic signal at a transducing location of the subject, and a sensor for receiving an attenuated acoustic signal at a sensing location of the subject. The attenuated signal received at the sensing location is digitized, and may be analyzed in the frequency and/or time domain. The comparison of the digitized attenuated signal against the initial transduced signal allows for the computation of the degree of acoustic attenuation between the transducing and sensing locations. Acoustic attenuation may be utilized to generate an intensity ratio. The ejection fraction of the heart subject may then be computed by correlation to the intensity ratio. Pulse echo methods are also disclosed. The echo transducer is oriented on the subject and generates a series of signal pulses. The return echo on the pulse is then received and a brightness encoded image is produced. The return echo provides location data on the internal structures of the subject including location, motion and speed.

The invention discloses a method for scanning ultrasonic microscope and measuring thickness, sound velocity, density and attenuation of a thin material simultaneously. The method includes: 1) the thin material is placed on the surface of a base material, an ultrasonic probe is located right above the base material and the thin material, ultrasonic echo signals s1 (t) and s2 (t) of the base material and the thin material are obtained; 2) deconvolution based on the wiener filtering and autoregressive spectral extrapolation technique is performed on the s2 (t) to obtain a signal h1 (t), and an initial value of acoustic transition time is selected; 3) initial values of other variables are selected, reflection coefficient frequency spectrum of the thin material is matched to obtain optimal values of acoustic impedance, acoustic transition time and acoustic attenuation coefficient of the thin material; 4) deconvolution based on the wiener filtering and autoregressive spectral extrapolation technique is performed on s1 (t)+s2 (t); and 5) the thickness, the sound velocity, the density and the attenuation of the thin material are calculated. Four-variable high-accuracy simultaneous measurement of the thin material can be achieved, and the problem of convergence domain is solved when the frequency spectrum is matched.

A structure having an area separation wall including: a first building unit; a second building unit; and an area separation wall having only outer membranes. Preferably, the area separation wall is fire resistance rated. The outer membranes provide acoustic attenuation without adversely affecting the fire resistance of the area separation wall. The area separation wall provides improved thermal resistance. In one embodiment, the area separation wall includes: an interior support structure and at least one outer membrane on each side of the interior support structure. The outer membranes provide acoustic attenuation. Between the outer membranes is a substantially organic material barrier. The structure may also include a tying structure connecting the area separation wall to the first unit and the second unit.

An ultrasonic liquid level detector includes clamp-on transducers for a liquid level measurement by the clamp-on transducers instead of insertion type transducers. The ultrasonic liquid level detector measures a height of a liquid-liquid interface or a gas-liquid interface based on an acoustic attenuation of an acoustic pulse or a transit-time of the acoustic pulse using a pulse echo technique or a combination thereof.

Accurately quantifying optical absorption coefficient using acoustic spectra of photoacoustic signals. Optical absorption is closely associated with many physiological parameters, such as the concentration and oxygen saturation of hemoglobin, and it can be used to quantify the concentrations of non-fluorescent molecules. A sample is illuminated by, for example, a pulsed laser and following the absorption of optical energy, a photoacoustic pressure is generated via thermo-elastic expansion. The acoustic waves then propagate and are detected by a transducer. The optical absorption coefficient of the sample is quantified from spectra of the measured photoacoustic signals. Factors, such as system bandwidth and acoustic attenuation, may affect the quantification but are canceled by dividing the acoustic spectra measured at multiple optical wavelengths.

A method and apparatus for biomedical subsurface imaging and measurement of thickness, elastic and optical properties of industrial and biomedical materials based on laser Photo-Thermo-Acoustic (PTA) frequency-swept heterodyne depth profilometry, In particular, the invention relates to biomedical imaging and measure of tissue and tumour thickness, L, speed of sound, c_s, acoustic attenuation coefficient, γ, optical absorption coefficient, μ_a, and optical scattering coefficient, μ_s. The method and apparatus involves providing for a sample of the material to be characterized; irradiating the material for a selected period of time with an excitation waveform from a modulated optical excitation source wherein a photo-thermo-acoustic emission is responsively emitted from said solid; detecting said emitted photo-thermo-acoustic emission; processing the electronic signal to convert the frequency-domain signal into time-domain and perform depth profilometric imaging and determining thermoelastic and optical properties of the material sample;

A kit for attenuation of noise includes a noise source audio transducer, two ear pieces, and a control unit. The two ear pieces have respective resilient bodies that engage outer portions of ear canals of respective ears of a user while respective in-ear transducers of the two ear pieces are respectively positioned in inner portions of the ear canals. The respective in-ear transducers detect discrepancies (e.g., incomplete superpositioning) between the noise and the anti-noise. The respective in-ear transducers optionally detect respective secondary path effects in the ear canals. The noise source audio transducer detects noise generated by a noise source (e.g., snoring noise). The control unit configures an adaptive filter based at least in part on an error signal, and optionally based in part on secondary path effects. The control unit generates signals representative of anti-noise. The two ear pieces produce the anti-noise responsive to the signals. The two ear pieces produce masking noise with sound level that varies in direct correlation with sound level of the noise generated by the noise source.

Vibro-acoustic attenuation or reduced energy transmission. The present invention relates to devices that display frequency zones of strong vibro-acoustic attenuation or reduced energy transmission. This can be used in particular, although not necessarily solely, in applications that require lightweight materials with good mechanical properties and good vibro-acoustic response or in applications that require materials with high sound reflection, absorption or sound isolation in a certain frequency band.

The present invention provides means of enhancing the acoustic attenuation and vibration damping of a material by (1) embedding a plurality of small particles of either a high characteristic acoustic impedance or a low characteristic acoustic impedance or combinations of high and low characteristic acoustic impedance materials to form a matrix material to act as a acoustic attenuator or vibration damper; and (2) combing this matrix material with a second layer of a decoupling material that serves to effectively isolate the matrix material and reduce its tendency to vibrate sympathetically to the impinging acoustic energy. The mass of the resultant material may be very low while retaining excellent acoustic attenuation, vibration damping, and structural characteristics.

The invention relates to an ultrasonic attenuation spectrum principle based method for measuring the average particle size and concentration of two types of mixed solid particles in a liquid or gas medium. The ultrasonic attenuation spectrum principle based method comprises the following steps of step 1, measuring an experimental measurement ultrasonic attenuation spectrum alpha (f) under the condition that the two types of solid particles A and B are located in a measurement area, wherein f is the ultrasonic frequency; step 2, calculating an acoustic attenuation coefficient Kext of the particle and acoustic wave effect; step 3, determining whether the particles are A particles or B particles and determining whether phonons are absorbed or scattered through the acoustic attenuation coefficient; step 4, calculating a scattering emergence angle theta M1 of the scattered phonons; step 5, continuing to calculate a theoretical ultrasonic attenuation spectrum through a result of the step 4; step 6, establishing an objective function according to the theoretical ultrasonic attenuation spectrum and the experimental measurement ultrasonic attenuation spectrum to solve the particle size and volume concentration. The ultrasonic attenuation spectrum based mixed solid particle size and concentration measurement method can be applied to the two types of mixed solid particles and laboratory scientific research and the online measurement and the application of the industrial field can be implemented.

A vented cover includes a pair of cross-flow ventilation ducts each including an acoustic noise reduction lining. The ducts are “cross-flow” in that they cross and bypass one another. The cover is affixed to an enclosure containing components of a computer system and abuts against a panel of the enclosure having an airflow aperture. An air moving device (AMD) passes air through the enclosure from the ducts if the cover is an intake cover, and/or into the ducts if the cover is an exhaust cover. The ducts increase the air path length, and the acoustic absorbing surface, thereby increasing acoustic attenuation. Airflow resistance is reduced by reducing surfaces perpendicular and close to the area where air enters and by reducing sharp turns in the ducts. The cover has a relatively thin depth because the ducts cross and bypass each other in a very space efficient manner.

In a helicopter gas turbine engine, lips (30, 32) defining a radial air intake (34) are connected along an opening (12a) of an engine compressor air supply passage (12). The air intake lips are at least partially formed by a sound attenuator (40, 42) calculated to attenuate sound frequencies produced by the compressor rotation.