Characterization and Design of a Non Ported Conventional Speaker for Acoustic Control

2005 ◽  
Author(s):  
Taehyun Shim
Keyword(s):  
Sound Pressure ◽  
Active Noise Control ◽  
Nonlinear Effects ◽  
Measured Data ◽  
Pressure Level ◽  
Design Procedures ◽  
Active Noise ◽  
Acoustic Control ◽  
Parameter Variations ◽  
Loud Speaker

A loud speaker has been widely used as a major actuator in the field of active noise control (ANC). In this paper, the design procedures for a non-ported conventional speaker that must meet restrictive size constraint as well as required sound pressure level at a targeted frequency for an acoustic control was presented. Dynamic model of a speaker that includes linear and nonlinear effects such as radiation resistance on speaker damping, voice coil electrical resistance has been developed and its responses were compared to measured data. The effects of speaker design parameter variations on a sound pressure and power consumption were also assessed experimentally and through simulation. It was found that the simulation results are well collated with experimental data and the desired objective has been met.

Active noise control system in a fire helmet – a proposal of the solution

2018 ◽  
Vol 558 (3) ◽  
pp. 11-15
Author(s):  
Leszek Morzyński ◽  
Grzegorz Szczepański
Keyword(s):  
Control System ◽  
Sound Pressure Level ◽  
Sound Pressure ◽  
Noise Control ◽  
Active Noise Control ◽  
Warning Signal ◽  
Verbal Communication ◽  
Pressure Level ◽  
Emergency Vehicle ◽  
Active Noise

An auditory warning signal emitted by a moving emergency vehicle is intended to inform other road users about an approaching emergency vehicle and the need to give way to it. Emission of a warning signal with the highest possible sound pressure level is the main method of ensuring the audibility and recognition of the warning signal by traffic participants at unknown and varying traffic noise, acoustic insulation of vehicles and noise in the interior of the vehicle. The A-weighted sound pressure level of the auditory warning signal reaching the interior of an emergency vehicle may exceed 90 dB, which can be harmful to the hearing, can adversely affect psychophysical fitness of the crew members and can significantly hinder verbal communication in the vehicle. This article presents the concept and results of numerical simulations of an active noise control system in fire helmets, which will reduce the exposure of the crew to the warning signal and improve the quality of verbal communication in an emergency vehicle. This system is integrated with the signal generation system. The Notch algorithm and the NLMS adaptation algorithm were used in the system's control algorithm. The construction of the controller was based on a microcontroller from the STM32F4 family.

scholarly journals First investigation on the applicability of an active noise control system on a tracked tractor without cab

2013 ◽  
Vol 44 (2s) ◽  
Author(s):  
Daniele Pochi ◽  
Roberto Fanigliulo ◽  
Lindoro Del Duca ◽  
Pietro Nataletti ◽  
Gennaro Vassalini ◽  
...  
Keyword(s):  
Sound Pressure Level ◽  
Digital Signal Processor ◽  
Sound Pressure ◽  
Engine Speed ◽  
Noise Control ◽  
Active Noise Control ◽  
Control Unit ◽  
Pressure Level ◽  
Maximum Speed ◽  
Active Noise

In last years, several research teams pointed their attention on the application of active noise control systems (ANC) inside the cabs of agricultural tractor, with the purpose of reducing the driver exposition to noise, that is only partially controlled by the frame of the cab. This paper reports the results of a first experience that aimed at verifying the applicability of an ANC on a medium-high power, tracked tractor without cab. The tested tractor was a Fiat Allis 150 A, equipped with rear power take off, used in the execution of deep primary tillage in compact soils. It is a tracked tractor without cab, with maximum power of 108.8 kW at 1840 min–1 of the engine. The ANC consists of a control unit box based on a digital signal processor (DPS), two microphones, two speakers and a power amplifier. The instrumentation used in noise data collecting and processing consisted of a multichannel signal analyzer (Sinus - Soundbook), a ½” microphone capsule and an acoustic calibrator, both Bruel & Kjaer. The study aimed at evaluating the behaviour of the ANC by means of tests carried out under repeatable conditions, characterized by pre-defined engine speed values. Three replications have been made for each engine speed. The sampling time was 30 s. Two series of tests were performed in order to compare the results observed with the ANC on and off. The engine speed adopted in the study ranged from 600 min– 1, up to 2000 min–1 (maximum speed) with steps of 100 min–1. The ANC proved to be effective in the interval of speed between 1400 and 1700 min–1, where the samplings have been intensified, adopting steps of 50 min–1. In such an interval, the attenuation observed with the ANC system on appeared evident both as weighed A sound pressure level (from 1.29 up to 2.46 dB(A)) and linear (from 4.54 up to 8.53 dB). The best performance has been observed at the engine speed of 1550 min–1, with attenuations, respectively of 2.46 dB(A) and 7.67 dB. Outside of the engine speed interval 1400 - 1700 min–1, the attenuations always resulted lower than 1 dB(A) for the weighed A sound pressure level and between 0.66 and 7.72 dB.

Development of Method for Measurement Sound Pressure Level to Use Earphone

2013 ◽  
Vol 717 ◽  
pp. 378-383
Author(s):  
Seok Hoon Kang ◽  
Hyuk Moon
Keyword(s):  
Hard Of Hearing ◽  
Sound Pressure ◽  
Measured Data ◽  
Pressure Level ◽  
Experimental Equipment ◽  
Warning Message ◽  
The Hours ◽  
Set Up ◽  
And Control ◽  
Widespread Dissemination

Earphone use has skyrocketed due to the widespread dissemination of portable acoustic-apparatus. As the result, hearing loss due to noise-induced is becoming a big social problem. As the existing method, warning message is only used to prevent the hard of hearing according to the earphone use. However, it is hard for users to know the effect of the hours of earphone use and volume on their hearing, and control the earphone use by themselves. Therefore, in this paper, the method is suggested that users measure the effect of the time and volume of earphone use on their hearing with the simple experimental equipment and program. The method suggested in this paper is based on the simple experimental equipment to set up the similar environment to the real ear, and the program to find out the effect on hearing with the measured data.

Delay-tuned combination-sensitive neurons in the auditory cortex of the vocalizing mustached bat

1988 ◽  
Vol 59 (2) ◽  
pp. 623-635 ◽  
Author(s):  
M. Kawasaki ◽  
D. Margoliash ◽  
N. Suga
Keyword(s):  
Auditory Cortex ◽  
Sound Pressure ◽  
Pressure Level ◽  
Target Range ◽  
Mustached Bat ◽  
Equivalent Effect ◽  
Loud Speaker ◽  
Cochlear Microphonic Potentials ◽  
Self Stimulation ◽  
Delay Tuning

1. FM-FM neurons in the auditory cortex of the mustached bat are sensitive to a pair of frequency-modulated (FM) sounds that simulates an FM component of the orientation sound and an FM component of the echo. These neurons are tuned to particular delays between the two FM components, suggesting an encoding of target range information. The response properties of these FM-FM neurons, however, have previously been studied only with synthesized orientation sounds and echoes delivered from a loud-speaker as substitutes for the bat's own orientation sounds and corresponding echoes. In this study, the combination sensitivity and delay tuning of FM-FM neurons were examined while the bat was actively vocalizing. 2. When the bat produced orientation sounds in an anechoic environment, or synthesized single FM echoes were delivered to a silent bat, the FM-FM neurons showed weak or no response. In contrast, when synthesized FM echoes were delivered with a particular delay from the FM component of the vocalized orientation sounds, the FM-FM neurons exhibited strong facilitative responses. 3. In both the vocalizing bats and the silent bats with substituted synthesized orientation sounds, all FM-FM neurons tested responded preferentially to the same echo harmonic (FM2, FM3, or FM4). 4. In vocalizing bats, FM-FM neurons showed maximum response to an echo FM component delivered with a particular delay (best delay) from an FM component in the orientation sound. Best delays measured with vocalized orientation sounds were nearly the same as those measured with synthesized orientation sounds. 5. The equivalent effect of a vocalized orientation sound and a synthesized FM1 component on the activity of FM-FM neurons indicates that, during echolocation, the FM1 component in the vocalized orientation sound stimulates the auditory system and conditions the FM-FM neurons to be sensitive to echoes with particular delays from the vocalized orientation sounds. 6. The amount of vocal self-stimulation to the inner ear by the bat's own vocalized sounds was measured by recording cochlear microphonic potentials (CMs). Spectral analysis of CM indicated that the amount of vocal self-stimulation by each harmonic of an orientation sound was equivalent to a sound of 70 dB sound pressure level (SPL) for the first harmonic (H1), 91 dB SPL for H2, 83 dB SPL for H3, and 70 dB SPL for H4, when the amplitude of the vocalized sound was 117 dB SPL at 5 cm in front of the bat's mouth.

scholarly journals Active Structural Acoustic Control of an Active Casing Placed in a Corner

2019 ◽  
Vol 9 (6) ◽  
pp. 1059 ◽  
Author(s):  
Anna Chraponska ◽  
Stanislaw Wrona ◽  
Jaroslaw Rzepecki ◽  
Krzysztof Mazur ◽  
Marek Pawelczyk
Keyword(s):  
Active Noise Control ◽  
Low Frequency ◽  
Frequency Noise ◽  
Noise Emission ◽  
Sound Sources ◽  
Low Frequencies ◽  
Emission Efficiency ◽  
Active Noise ◽  
Acoustic Control ◽  
Device Noise

Electric appliances used in workplaces and everyday life often generate a low-frequency noise, which affects human body systems. Passive methods employed to reduce noise are not effective at low frequencies. The classical approach to active noise control practically involves the generation of local zones of quiet, whereas at other areas the noise is reinforced. Moreover, it usually requires a large number of secondary sound sources. Hence, an active casing approach has been developed. The active casing panels’ vibrations are controlled to reduce the device noise emission. Efficiency of this method has been previously confirmed by the authors and the results have been reported in multiple journal publications. However, in the previous research experiments, the active casing was placed at a distance from the enclosure walls. In this research, the active casing is located in a corner and such placement is intentionally used to facilitate the active control system’s operation. The noise reduction performance is investigated at multiple configurations, including a range of distances from the corner and different error microphone arrangements. The analysis of both primary and secondary paths is given. Advantages and drawbacks of different active casing configurations are presented and discussed.

A Study on the Far-Filed Sound Pressure Level of Rectangular Plate Based on Fourier Transform

2013 ◽  
Vol 753-755 ◽  
pp. 1779-1784
Author(s):  
Ren Wen Dai ◽  
De Shi Wang ◽  
Yong Yong Zhu
Keyword(s):  
Fourier Transform ◽  
Rectangular Plate ◽  
Sound Pressure Level ◽  
Sound Pressure ◽  
Active Noise Control ◽  
Pressure Level ◽  
External Excitation ◽  
Approximation Solution ◽  
Transform Method ◽  
Line Force

The far-filed approximation solution was derived in a closed formula by using Fourier transform method. Two kind of possible concentrated forces, a line force, a point force, were included in the analysis. Moreover, a parametric study was carried out to clarify the effect of the incentive loading position and the various physical characteristics parameters of the rectangular plate. Conclusion is drawn that, the far-filed pressure level decreased with external excitation approached to the edge. Through analysis on far-filed sound pressure level, that can give foundation of designing acoustical elements and active noise control.

Active Noise Control to Reduce the Blade Tone Noise of Centrifugal Fans

1988 ◽  
Vol 110 (3) ◽  
pp. 377-383 ◽  
Author(s):  
G. H. Koopmann ◽  
W. Neise ◽  
W. Chen
Keyword(s):  
Sound Pressure ◽  
Noise Control ◽  
Control Method ◽  
Reference Signal ◽  
Active Noise Control ◽  
Perforated Plate ◽  
Aerodynamic Noise ◽  
Secondary Sources ◽  
Active Noise ◽  
Centrifugal Fans

This paper describes an active noise control method to suppress the blade tones of centrifugal fans. Two secondary sound sources are mounted into the cutoff region of the fan casing. These sources are driven with electrical signals that are synchronized with the rotation of the impeller, and their amplitudes and phase are adjusted to give maximum reduction for the blade tone levels in the inlet and outlet duct of the fan. With this design, the sound emitted by the secondary sources is introduced into the interior of the casing near the source region where the blade tone is generated, i.e., the cutoff. The present experiments were concentrated on the reduction of the fundamental of the blade tone for centrifugal fan with impeller diameters between 280 mm (11 in.) and 710 mm (28 in.). Two different designs of secondary sources were investigated. In the first, two loudspeakers are contained within an enclosure which has an open end made of a curved perforated plate which replaces part of the original cutoff. The second design incorporates two vibrating plates which replace portions of the outlet duct side and the volute side of the cutoff. Reductions in tone sound pressure level of up to 23 dB have been observed for a variety of aerodynamic loading conditions and fan inlet geometries. To obtain a better understanding of the physical mechanism of this active noise control method, sound pressure measurements were also made on the inner surface of the fan casing along the volute. Both amplitude and phase of the blade passing frequency component were measured relative to a reference signal derived from the impeller rotation. The result of this experiment is that the sound field inside the casing is dominated by the pressure pattern rotating together with the impeller. Since the impeller tip Mach number is well below sonic speed, however, the radiation efficiency of the rotating pressures is very low. The blade tone noise measured in the far-field is generated by the unsteady pressures at the cutoff which in turn are produced by the flow leaving the impeller. This aerodynamic noise generating mechanism is modified by the active sources located in the cutoff.

scholarly journals Active structural-acoustic control of interior noise in a vibro-acoustic cavity incorporating system identification

2017 ◽  
Vol 36 (3) ◽  
pp. 261-276 ◽  
Author(s):  
Ashok K Bagha ◽  
Subodh V Modak
Keyword(s):  
Kalman Filter ◽  
System Identification ◽  
Noise Control ◽  
Active Noise Control ◽  
State Observer ◽  
Linear Quadratic ◽  
Linear Quadratic Gaussian ◽  
Active Noise ◽  
Acoustic Control ◽  
Structural Acoustic Control

Linear quadratic Gaussian optimal control is one of the techniques used for active noise control. In practical implementation of this technique, one of the key difficulties faced is the estimation of the states of the plant. A state observer that accurately estimates these states can be used in this regard. Studies reported make use of analytically or experimentally derived models to build observers. This paper proposes a method for active noise control in the framework of active structural-acoustic control incorporating system identification for the development of the linear quadratic Gaussian controller. Kalman filter is used as a stochastic state observer of the plant states. System identification is carried out using modal testing and finite element model updating to obtain an accurate model of the plant for building up the Kalman filter. The objective of the proposed method is to actively reduce the noise inside the cavity due to disturbances acting on the cavity structure. The active control is achieved by controlling the structural vibrations by taking into account the degree of coupling between the various structural and the acoustic modes. The effectiveness of the proposed method is evaluated experimentally on a 3D rectangular box cavity with a flexible plate.

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