Showing papers on "Sound power published in 2000"

Radiation modal expansion: Application to active structural acoustic control

Abstract: This paper demonstrates active structural acoustic control using multiple input/output adaptive sensoriactuators combined with radiation filters and a feedback control paradigm. A new method of reduced order modeling/design of radiation filters termed radiation modal expansion (RME) is presented. For the experiments detailed in this paper, the RME technique reduced the modeling of the radiation matrix from 400 transfer functions to 6 transfer functions (multiplied by a constant transformation matrix). Experimental results demonstrate reductions of radiated sound power on the order of 5 dB over the bandwidth of 0–800 Hz.

Sound system and method for creating a sound event based on a modeled sound field

Abstract: A sound system and method for modeling a sound field generated by a sound source and creating a sound event based on the modeled sound field is disclosed. The system and method captures a sound field over an enclosing surface, models the sound field and enables reproduction of the modeled sound field. Explosion type acoustical radiation may be used. Further, the reproduced sound field may be modeled and compared to the original sound field model.

Multiple frequency cleaning system

Abstract: The invention utilizes multiple frequency sound in liquids to improve the cleaning or processing effect. The sound frequencies are produced in two or more non-overlapping continuous frequency ranges. The sound frequencies are controlled to change frequency within the frequency ranges and the sound frequencies are programmed by a digital code to jump amongst the frequency ranges. The sound frequencies may change continuously within the frequency ranges, and the sound frequencies may jump discontinuously from one frequency range to another. The frequency ranges may also be within different, non-contiguous and non-overlapping frequency bands.

Method and apparatus for concurrently estimating respective directions of a plurality of sound sources and for monitoring individual sound levels of respective moving sound sources

Abstract: A method and apparatus enabling information including respective angular directions to be obtained for one or more sound sources includes a sound source direction estimation section for frequency-domain and time-domain processing of sets of output signals from a microphone array to derive successive estimated angular directions of each of the sound sources. The estimated directions can be utilized by a passage detection section to detect when a sound source is currently moving past the microphone array and the direction of the sound source at the time point when such passage detection is achieved, and a motion velocity detection section which is triggered by such passage detection to calculate the velocity of the passing sound source by using successively obtained estimated directions. In addition it becomes possible to produce directivity of the microphone array, oriented along the direction of a sound source which is moving past the microphone array, enabling accurate monitoring of sound levels of respective sound sources.

Apparatus and method for transmitting sound

Abstract: An apparatus and method for transmitting sound are provided. The apparatus includes an external sound receiver for receiving external sounds and converting them into an external sound signal, a volume controller for outputting sound signals only if each of the volumes of the sound signal of a sound producing device and the sound signal of the external sound receiver exceeds a predetermined reference level, and a mixer for mixing the sound signal of the sound producing device with the sound signals output from the volume controller and outputting the result. The apparatus mixes ambient sounds having volume exceeding a certain volume with the sound of a sound producing device and transmits the mixed sounds to a pair of headphones which are a sound receiver for a user, thereby allowing the user to hear an ambient alarm sound while the user is listening to the sound of the sound producing device and making it possible for the user to audibly detect danger. Consequently, the apparatus provides user safety.

Method for determining the depth values of a body of water

Abstract: For mapping and exploring bodies of water, fan depth finders are used that emit ultrasound pulses and receive-echo pulses in a number of tightly-bundled receiving sectors. Because the predominant number of receiving directions is oriented diagonally downward instead of straight down, these ultrasound pulses propagate on bent paths due to sound refraction. Sound refraction is caused by different sound velocity layers, the precise knowledge of which is necessary for determining an average sound velocity. The method of the present invention does not require a separate measuring probe to measure the sound velocity at different depths; rather, the average sound velocity is determined using a regression method based on the travel time measurements of the ultrasound pulses. In this method, first the floor profile that forms the basis of the measured travel times is determined with an assumed average sound velocity and compared with a floor profile model composed of partial functions modeled in a specific manner. Because a correction value for the average sound velocity can be determined from the partial functions, improved depth values of the floor profile can be determined iteratively with the measured travel times and the corrected sound velocity. A method of this type can advantageously be implemented on research and survey vessels for attaining the high precision required in surveying technology.

Measurement of acoustic streaming using magnetic resonance.

Abstract: Magnetic resonance imaging (MRI) has been used to explore acoustic streaming caused in water under ultrasonic exposure conditions similar to those used for diagnostic applications. Streaming was established in an enclosed tube with acoustically transparent end windows, using a pulsed, weakly-focused transducer of acoustic frequency 3.5 MHz. Phase-detection MRI was used to image and quantify streaming profiles in the region of the acoustic focus. Acoustic powers in the range 0.4 mW to 100 mW were used. The sensitivity of the technique enabled streaming velocities down to 0.1 mm s−1 to be measured, generated by acoustic power less than 1 mW. In addition, acoustic streaming generated within open meshes with minimum pore dimensions of 3.0 mm and 2.0 mm was measured. The flow velocity in the coarser mesh reached 0.9 mm s−1 at 95 mW total acoustic power. These observations demonstrate that acoustic streaming is probably a much more general phenomenon in diagnostic ultrasound (ultrasound) than previously recognised. The combination of magnetic resonance and ultrasound shows promise as a diagnostic method for the differentiation of cystic lesions in vivo, and for their characterisation, with sensitivity significantly greater than using ultrasound alone.

Road traffic noise prediction model 'asj model 1998' proposed by the acoustical society of japan - part 2: calculation model of sound power levels of road vehicles

Abstract: The calculation formulae for the sound power levels of road vehicles adopted in the ASJ Model 1998 have been introduced. The relationship between running speed and sound power level on urban roads is much different from that on freeways. On freeways and urban roads under steady running conditions in the speed range higher than 40 km/h, the expression of 30log10V is adopted as the speed dependence. On the other hand, for the case of urban roads where vehicles accelerate and decelerate in the speed range lower than 60 km/h, the expression of 10log10V is adopted. For the covering abstract see ITRD E107776.

A device for active sound control in a space

Abstract: The invention refers to a device for sound control in a space (2) with a sound field from at least one sound source (3). The device includes a pulse sensor (5), which provides a pulse signal from the sound source (3). Moreover, the device includes a number of sound influencing members (8) for reducing the sound field in the space (2) and a number of sound sensors (9), which sense the actual sound field in the space and provide an error signal. A control unit includes a signal supplied device (11, 12), which receives a pulse signal and supplies a first signal to an adaptive filter (15). The filter has a number of filter coefficients and generates a drive signal for each sound influencing member (8). The signals supply device also supplies second signals to a calculating member (24), which calculates the value of the filter coefficients by the second signals and the error signals for updating the adaptive filter (15). A detecting member detects phase and frequency of the pulse signal and a coefficient table provides two sets of coefficients for generating the second signals from detected phase and frequency of the pulse signal.

Sound field reproducing method and apparatus for the same

Abstract: A space surrounding a sound source (S) which is set in a sound field (10) to be reproduced is divided into sound source element regions (S1 to Sn), and a space surrounding a sound receiving point (R) is divided into sound receiving element regions (R1 to Rm). An impulse response when a sound radiated from the sound source (S) is emitted from one of the sound source element regions (S1 to Sn), passes through the sound field (10), enters one of the sound receiving element regions (R1 to Rm), and then reaches the sound receiving point (R) is obtained for each of combinations of the sound source element regions (S1 to Sn) and the sound receiving element regions (R1 to Rm). A sound emitted from a real sound source (Sr) in an arbitrary real space (26) is picked up by microphones (MC1 to MCn) placed correspondingly with the sound source element regions (S1 to Sn). In an FIR matrix circuit (42), the pickup signals are respectively subjected to a convolution operation with impulse responses which are obtained for each of the sound source element regions (S1 to Sn) in corresponding directions.

Sound generation device for automobile passenger compartment has signal sources providing engine operating noise coupled to sound conduction system via sound chambers

Abstract: The sound generation device has signal sources (5), providing noise which represents the operation of the automobile engine (4), coupled to a sound conduction system (7,8,10), for feeding the sound waves to the interior of the automobile passenger compartment (2), via respective sound chambers (6).

Sound propagation and speech transmission in a branching underground tunnel.

Abstract: The characteristics of sound propagation and speech transmission along a tunnel with a “T” intersection were investigated. At receivers within sight of the sound source, low frequencies were mainly attenuated around the intersection than high frequencies. At receivers out of sight of the source, high frequencies were extensively attenuated. The overall pattern of sound attenuation along the different sections of tunnel, which was calculated by the conical beam method, agreed well with the measurements in this study. Numerical calculations of reflected and diffractedwaves with minimum transmission paths in a two-dimensional plane showed that reflected waves were the primary contributors to sound fields out of sight of the source. The articulation scores measured at receivers within sight of the source were high, and most of the confusion concerned syllables that could easily be misheard, even if there were a high signal-to-noise ratio. The types of syllable confusions observed at the receivers out of sight of the source appeared to have been caused by the greater deterioration in speech signals along this part of the tunnel, especially at high frequencies. The evaluation by rapid speech transmission indices (RASTI) appeared to be overestimated at the receivers out of sight of the source. Taking into account the early decay times of impulsive sound and the calculation procedures used in RASTI, it is concluded that speech intelligibility may not have been evaluated correctly by RASTI.

Measurement techniques for the acoustic analysis of synchronous belts

Abstract: At present, in the automotive field, the noise generated by belt drives is evaluated by using microphones in the proximity of the belt, crankshafts, idlers and so on. Such a method can be misleading, since it may easily include the contributions of other noise sources present during the measurement. Moreover, a large amount of data is needed in order to test various layouts and various running conditions. We present a method for the analysis and prediction of the noise generated by belt drives which consists of two distinct phases in this paper. For simplicity, a two-pulley belt drive has been considered and the results have been validated at the meshing frequency, at which, as has been shown in the existing literature, the phenomenon of noise generation is mainly concentrated. In the first stage of the work, the acoustic power generation of the belt drive being tested was measured by means of acoustic intensity techniques. Subsequently, an acoustic prediction was performed by using vibration data obtained with a scanning laser Doppler vibrometer (SLDV) as inputs for a boundary element code. The SLDV was used because of its capability of measuring in-operation data on the running belt, which would not have been possible using traditional contact sensors (accelerometers and so on). The results obtained in the two phases were finally compared in order to evaluate the relation between the vibratory behaviour and the total acoustic radiation determined experimentally. The experimental and numerical data agree fairly well, adding precious information on the noise generation mechanisms and showing the feasibility of modelling the vibro-acoustic behaviour of belt drives and the possibility of a totally numerical procedure. In particular the implementation of an entirely numerical procedure using, for example, data generated through the use of codes for the dynamic characterization of mechanical systems (multi-body mechanical models and so on) seems foreseeable. In the final section of the present work, the uncertainty arising from the measurement processes of the investigation method presented is also discussed.

Absorption of Sound near Abrupt Area Expansions

Abstract: Sound incident onto an abrupt area expansion in a channel is investigated both numerically and analytically. In the presence of a mean e ow, the incident sound leads to unsteady vortex shedding from the lip of the expansion, thereby converting acoustic into vortical energy. We use an acoustic analogy and Green' s functions to determine the sound ree ected and transmitted across the area change. We compare predictions obtained from threedifferent Green' sfunctionswithsourcetermsderivedeitherusinga simpleanalyticalmodelorfrom anumericalcalculation. Thecompact Green' s function, with zero normalderivative on theductwalls, givesthe bestresultsfora low-Mach- number e ow. This Green' s function contains a singularity at the lip of the expansion (and hence acoustic sources neartheliphavethegreatesteffect ).Thismeansthatourestimateoftheoverallvorticitye eldcanberelativelycrude, when using the compact Green' s function, provided it is accurate near the lip. Therefore, although predictions for the radiated sound e eld made using all three Green' s functions are formally correct, the solution made using the compact Green' s function is less susceptible to errors in the source terms and gives more accurate results. In addition, we e nd that thereisa Strouhal number at which sound absorption is maximized and that this absorption can be enhanced by multiple ree ections from the duct ends. Our predictions are compared with an experiment. In this paper we investigate this energy exchange for a simple two-dimensional e ow past a backward-facing step with e ow using anacousticanalogyfromHowe 14 torelatetheacousticsourcestothe shed vorticity. Initially, we consider two semi-ine nite channels of heighth and H(h < H) joinedat y1 = 0.There is a mean e ow along the channelthatseparatesatthe rearward-facing step.Wedetermine the transmission and ree ection of an incident sound wave atthe step including the effects of the mean e ow. This problem is investigated both numerically and analytically. Vortex-sound interaction is of fundamental interest in aeroacous- tics, and this simple geometry enables us to investigate solution techniques and compare theoretical results with experiment. To re- late the sources from the acoustic analogy to the sound that radiates away from the junction, we must introduce a suitable Green' s func- tion for the pipework system. The choice of Green' s function is crucial to the solution, and three different Green' s functions are cal- culated.Two ofthesearederivedfromexpansionsintermsofmodes of straight-walled semi-ine nite pipes, whereas the remaining one, the compact Green' s function, satise es boundary conditions of zero normal velocity on all rigid surfaces. The compact Green' s function has a singularity at the lip of the expansion, and so sources near the lip have a greater effect on the sound that radiates to the far e eld than those farther away. This is important because it implies that, when using the compact Green' s function, our prediction for the vorticity e eld, whether from an analytical model or from a numer- ical calculation, can be relatively crude provided that the vorticity near the lip is accurately predicted. As a result, we postulate that the most accurate results will be obtained using the compact Green' s function. The calculation of these Green' s functions is discussed in Sec. III. The vorticity e eld is obtained in two ways: using an analytical model (Sec. IV.A) and using computational e uid dynamics (CFD; Sec. IV.B) with comparison between the two. The analytical model that we use for the vorticity is that of Howe 17 and assumes that the strength of the shed vorticity is unchanged as it convects down- stream and it forms an ine nitely thin vortex sheet whose strength is determinedbytheapplicationoftheKuttacondition.Incontrast,our numerical calculation uses a crude zero-equation turbulence model and the strength of the vorticity diffuses and decays as it convects downstream as a result of numerical diffusion. Despite the apparent differences between the two models, we show in Sec. V that the radiated sound e elds, which they predict, are very similar because of the importance of the region near the lip, provided the compact Green' s function is used in the calculation of the far-e eld sound. Our initial calculations are for two semi-ine nite pipes, but pre- dictions for e nite length pipes are obtained in Sec. VI by the in- troduction of a ree ection coefe cient at the pipe exit. Solutions for e nite length channels are easily derived from the ine nite channel solutions, which isimportant because it implies that, fora particular expansion ratio and Mach number, the ine nite channel solution is all that is required; the solution for any length channel can then be deduced from this. We justify our results by comparison with an experiment and discuss the implication for the absorption of incident sound waves. In particular, we e nd, for ine nite channels, there is an optimum Strouhal number at which maximum absorption is achieved. When wave ree ection from the ends of e nite length pipes is included, channel resonances can amplify this absorption.

Road traffic noise prediction model 'asj model 1998' proposed by the acoustical society of japan - part 1: its structure and the flow of calculation

Abstract: The Acoustical Society of Japan published a new prediction model of road traffic noise, "ASJ Model-1998", in which the equivalent continuous A-weighted sound pressure levels LAeq in roadside areas can be predicted based on energy-base calculation. This method consists of the models of sound power levels of road vehicles under stable and unstable running conditions, two kinds of sound propagation calculation methods, corrections for ground absorption, meteorological effects, shielding effects of roadside buildings, etc. In this paper, the outline of the model and the main flow of the prediction calculation are introduced. For the covering abstract see ITRD E107776.

Active control of turbulent‐boundary‐layer‐induced sound radiation from aircraft style panels

Abstract: The results of active control of TBL‐induced sound radiation will be presented. In this test, a panel was constructed similar to the sidewall of an aircraft; however, the panel was flat to allow a simple incorporation into the wind tunnel wall. The static in plane stress normally associated with aircraft cabin pressurization (at 40 000 ft) was provided via a tensioning fixture. Thus the smooth ‘‘exterior’’ side was subjected to TBL flow inside the tunnel, and the other (interior) side radiated sound into the model preparation room. Accelerometers were mounted on the interior side of the panel, and microphones were positioned in the model preparation room to monitor sound radiation. Experiments were conducted at both Mach 0.8 and Mach 2.5 flow conditions, and active control was performed on a single bay, and two bays. The results demonstrate reductions in total radiated sound power on the order of 10–15 dB at resonances, and 5–10 dB integrated over the band width of 150–800 Hz. This work represents the first known demonstration of ASAC of aircraft‐style panels subjected to both subsonic and supersonic flows.

Optical methods for selectively sensing remote vocal sound waves

Abstract: Methods for remotely sensing sound waves in an optically transparent or semitransparent medium through detecting changes in the optical properties of the medium, which are caused by the sound waves. For example, to implement a microphone that can sense sound at a distance from the sound source. The variations in the attenuation or the phase of a beam of light that is received after passing through the sound waves are sensed and converted to an electrical or other signal. For the attenuation method, the wavelength of the beam of light sensed is selected to be one that is highly attenuated by a constituent of the medium, so that the changing instantaneous pressure of the medium due to the sound pressure waves can be detected through the changing light attenuation due to the changing density of the air along the light path. For the phase shift method, the velocity of light, and therefore its phase is changed by the changing density of the air due to the sound waves, and this can be detected through interferometric means.

Sound pickup device, sound pickup and sound source separating device and method for picking up sound, method for picking up sound and separating sound source and recording medium for recording sound pickup program, sound pickup and sound source separating program

Abstract: PROBLEM TO BE SOLVED: To separate and extract individual sound sources by inferring a sound source direction, using two bidirectional microphones and one omnidirectional microphone, and switching zones without having to move the microphone physically. SOLUTION: A sound pickup and sound source separating device comprises a plurality of directional microphones 1, 2 of directions for different directivities from each other, one omnidirectional microphone 3, a directivity-varying means 4 for generating a signal obtained by weighted summing by a weighted summing coefficient set in different combinations of directions of the directivity, based on sound pickup signals from the respective microphones, a sound source direction inferring means 7 for inferring the sound source direction, based on the signal obtained by weighted summing the respective weighted summing coefficients, and a directivity-selecting means 6 for selecting the weighted signal by the weighted summing coefficient based on the inferred sound source direction.