Structural-acoustic coupling and psychophysical effects in the active control of noise in vehicles

Active noise control systems offer a potential method of reducing the weight of passive acoustic treatment and, therefore, increasing vehicles' fuel efficiency. These can be particularly cost-efficient if integrated with the entertainment system. A combined system is presented employing feedforward control of engine noise and feedback control of road noise, using a `modal' error signal. Due to the dependence of the feedback system on the modal response of the vehicle cabin, the influence of structural-acoustic coupling on this response and the consequent effects on the control performance are investigated. Simulations of the performance of the control systems in rigid and non-rigid enclosures show that the feedforward component is largely unaffected by structural-acoustic coupling, whilst the modal feedback performance is reduced by 3 dB due to the shift in the frequency of the targeted acoustic mode. The simulation results are confirmed through experiments conducted in a structural-acoustic coupled enclosure

Review of active noise control techniques with emphasis on sound quality enhancement

The traditional active noise control design aims to attenuate the energy of residual noise, which is indiscriminative in the frequency domain. However, it is necessary to retain residual noise with a specified spectrum to satisfy the requirements of human perception in some applications. In this paper, the evolution of active noise control and sound quality are briefly discussed. This paper emphasizes on the advancement of active noise control method in the past decades in terms of enhancing the sound quality

Determination and evaluation of clinically efficient stopping criteria for the multiple auditory steady-state response technique

Background: Although the auditory steady-state response (ASSR) technique utilizes objective statistical detection algorithms to estimate behavioural hearing thresholds, the audiologist still has to decide when to terminate ASSR recordings introducing once more a certain degree of subjectivity. Aims: The present study aimed at establishing clinically efficient stopping criteria for a multiple 80-Hz ASSR system. Methods: In Experiment 1, data of 31 normal hearing subjects were analyzed off-line to propose stopping rules. Consequently, ASSR recordings will be stopped when (1) all 8 responses reach significance and significance can be maintained for 8 consecutive sweeps; (2) the mean noise levels were ≤ 4 nV (if at this “≤ 4-nV” criterion, p-values were between 0.05 and 0.1, measurements were extended only once by 8 sweeps); and (3) a maximum amount of 48 sweeps was attained. In Experiment 2, these stopping criteria were applied on 10 normal hearing and 10 hearing-impaired adults to asses the efficiency. Results: The application of these stopping rules resulted in ASSR threshold values that were comparable to other multiple-ASSR research with normal hearing and hearing-impaired adults. Furthermore, in 80% of the cases, ASSR thresholds could be obtained within a time-frame of 1 hour. Investigating the significant response-amplitudes of the hearing-impaired adults through cumulative curves indicated that probably a higher noise-stop criterion than “≤ 4 nV” can be used. Conclusions: The proposed stopping rules can be used in adults to determine accurate ASSR thresholds within an acceptable time-frame of about 1 hour. However, additional research with infants and adults with varying degrees and configurations of hearing loss is needed to optimize these criteria

Acoustic Design Criteria in Naturally Ventilated Residential Buildings: New Research Perspectives by Applying the Indoor Soundscape Approach

The indoor-outdoor connection provided by ventilation openings has been so far a limiting factor in the use of natural ventilation (NV), due to the apparent conflict between ventilation needs and the intrusion of external noise. This limiting factor impedes naturally ventilated buildings meeting the acoustic criteria set by standards and rating protocols, which are reviewed in this paper for residential buildings. The criteria reflect a general effort to minimize noise annoyance by reducing indoor sound levels, typically without a distinction based on a ventilation strategy. Research has developed a number of solutions, discussed here, that try to guarantee ventilation without compromising façade noise insulation, but, currently, none have been adopted on a large scale. This concept paper highlights the main limits of the current approach. First, a fragmented view towards indoor environmental quality has not included consideration of the following acoustic criteria: (i) how buildings are designed and operated to meet multiple needs other than acoustical ones (e.g., ventilation, visual, and cooling needs) and (ii) how people respond to multiple simultaneous environmental factors. Secondly, the lack of a perceptual perspective has led acoustic criteria to neglect the multiple cognitive and behavioral factors impinging on comfort in naturally ventilated houses. Indeed, factors such as the connection with the outside and the sense of control over one’s environment may induce “adaptive acoustic comfort” opportunities that are worth investigating. The mere use of different sound level limits would not be enough to define criteria tailored to the complex user–building interaction that occurs under NV conditions. More holistic and human-centered approaches are required to guarantee not only neutrally but even positively perceived indoor acoustic environments. For this reason, this paper considers this apparent conflict from a soundscape viewpoint, in order to expose still unexplored lines of research. By underpinning a perceptual perspective and by contextualizing it, the indoor soundscape approach provides a framework capable of overcoming the limits of the traditional noise control approach. This could provide the opportunity to foster a wider adoption of NV as a passive design strategy that enhances user health and well-being, while enabling low-cost, and low-energy cooling and ventilation, thereby contributing to current climate change challenge

From sound quality to sound systems: a retrospective study

The current socio-technological context encourages the increase of products with increasingly complex and advanced interfaces. Sound is a valuable resource capable of facilitating interaction between product and user, and conveying information about events of different nature and criticality.However, design engineering lacks unified knowledge and a consensus methodology that facilitates the characterization of sound during product development processes. This article presents a retrospective, critical and systematic review of the most relevant theoretical and practical contributions applied in design engineering, from different scientific perspectives. The result is a map of publications classified in 6 large blocks, ranging from initial psychoacoustic studies, through observations on sound semantics, to the most up-to-date approaches supported by communication theories. In this way, researchers and developers in design engineering are provided with a guide and introduction to the main key aspects of sound study and in its application to product design domain. The article collects the main bibliographical references indicating whether they are theoretical or experimental studies, the scientific field with which they relate, their chronological location, and highlighting their main contributions

Multi-physics phenomena influencing the performance of the car horn

Usually cars are equipped with disk horns. In these devices electromagnetic energy is converted into mechanical energy of two nuclei that vibrate and impact each other \u2013 the impacts excite the disk that radiates sound. This paper aims at understanding the results of acoustic tests carried out on horns with different excitation voltages and different mounting brackets. Since many non-linear phenomena are inherent in the vibrations of the nuclei, a detailed model of the electromechanical system is developed. Results show the dependence of operating frequency on the input voltage and the role played by the various mechanical and electrical parameters on the dynamics of the horn. Particular nonlinear effects, like sub-harmonic excitation, are presented and discussed. A general agreement between experimental results and numerical simulations is found

Aeronautical Engineering. A continuing bibliography with indexes, supplement 156

This bibliography lists 288 reports, articles and other documents introduced into the NASA scientific and technical information system in December 1982

DESIGN AND EVALUATION OF PORTABLE PSYCHOACOUSTIC TESTING SYSTEMS

There is an increasing demand for developing portable psychoacoustic testing systems to evaluate the hearing abilities of people. In this thesis, the design, development, and evaluation of portable, flexible, and versatile wired and wireless psychoacoustic testing systems will be presented. The design of the wired system utilizes a USB audio I/O controller chip for communicating with the application software on the host through a USB cable. The wireless system includes two units: a transmitter and a receiver. 2.4GHz RF transceiver chips are employed for wireless communication. Double-side PCBs populated with 0603 SMD were designed and fabricated. To go along with the hardware, software was developed on a handheld device to control and execute several psychoacoustic tests and to log subjective data. Objective measurements and small scale clinical trials were undertaken to test the efficiency of the proposed portable systems

Subjective listening experiments for annoyance investigation

Noise limits and guidelines that consider only the sound pressure level or the loudness of noises are not efficient in protecting people from all the adverse effects of noise. Other physical characteristics, e.g., tonality, modulation, and frequency content, should also be considered, especially when the noise level is low and it cannot cause hearing risk, but might lead to annoyance and disturbance. Annoying noises have an impact on health and well-being, but this impact and its relationship with the physical properties have not been sufficiently studied. Subjective annoyance caused by noises like those we experience in living spaces and offices should be further investigated via psychoacoustic laboratory experiments. The primary aim of this work was to develop systematic, effective, and reliable methodology to perform this type of psychoacoustic tests. The secondary aim was to investigate the objective metrics that best predict subjective annoyance in four typical noise conditions: ventilation noise in office spaces, traffic noise in homes, neighbors’ noise in homes, and noises with tonal components in homes. The main result was the development of the methodology, which in turn enabled us to define our own standards and guidelines. Furthermore, we identified the objective metrics that best correlated with subjective annoyance in each one of the four studied noise situations. In offices, five metrics predicted subjective ratings reasonably well. Noise with sound energy at higher frequencies was less tolerated. Noise with a slope of -7 dB per octave band increment resulted in the highest satisfaction. In dwellings, related to neighbors’ living sounds, four metrics of airborne sound insulation performed well to predict annoyance. We demonstrated that 50–80 Hz bands should not be included in the objective rating. In dwellings, related to five types of traffic noise transmitted through façade elements, one metric Rw+C50–3150 performed significantly better than the others. The last experiment proved that tonality is not properly considered in current standards and noise guidelines. The performed psychoacoustic research demonstrated that other physical properties than the sound pressure level should be considered when assessing noise annoyance, and it provided evidence to the objective metrics that would make noise guidelines more efficient with respect to health protection.Subjektiivisia kuuntelukokeita häiritsevyyden tutkimiseksi Melurajat ja ohjeet suojelevat ihmisiä melun haitallisista vaikutuksista, mutta ne ottavat enimmäkseen huomioon vain melun äänenpainetason tai voimakkuuden. Muut fyysiset ominaisuudet, kuten kapeakaistaisuus, modulaatio ja taajuussisältö, joilla on selvä vaikutus subjektiiviseen kokemukseen ja häiritsevyyteen, jätetään usein huomiomatta. Ärsyttävät äänet saattavat noudattaa lakia niiden kielteisistä vaikutuksista huolimatta, koska niiden äänenpainetaso ei ylitä yhtään melurajaa. Asuintilojen ja toimistojen melun aiheuttamaa subjektiivista ärsytystä tulisi tutkia tarkemmin psykoakustisten laboratoriokokeiden avulla. Työn ensisijaisena tavoitteena oli kehittää järjestelmällinen, tehokas ja luotettava menetelmä tämän tyyppisten psykoakustisten testien suorittamiseksi. Lisäksi selvitettiin, mitä muita objektiivisia mittareita, kuin äänenpainetaso tai äänenvoimakkuus, ennustavat parasta subjektiivista ärsytystä ja häiritsevyyttä. Työssä tutkittiin neljää tyypillistä meluolosuhdetta: toimistotilojen ilmanvaihdonääniä, kaupungin liikenteen melua kodeissa, naapurin melua kodeissa, ja kapeakaistaisia komponentteja sisältävää melua. Päätuloksena oli menetelmän kehittäminen, joka mahdollisti omien standardien ja toimintaohjeiden määrittämisen. Lisäksi tunnistettiin objektiiviset mittarit, jotka korreloivat paremmin subjektiivisen häiritsevyyden kanssa kussakin neljästä tutkitusta melutilanteesta. Toimistoissa viisi mittaria ennusti kohtuullisen hyvin subjektiivisia luokituksia. Kohinaa, joka kuului korkeammilla taajuuksilla toimivalla äänenergialla, siedettiin vähemmän. Asunnoissa, kun asumisääniä syntyy naapurin asunnossa, neljä ilmaääneneristysmittaria toimi hyvin ennustamaan asukkaiden subjektiivista ärsytystä. Osoitettiin, että 50–80 Hz: n kaistoja ei pitäisi sisällyttää objektiiviseen luokitukseen. Myös asunnoissa, liittyen viitteen eri liikennemeluun kantautumassa sisätilaan julkisivuelementtien kautta, yksi metrinen Rw+C50–3150 toimi huomattavasti paremmin kuin muut. Viimeinen koe osoitti, että tonaalisuutta ei oteta asianmukaisesti huomioon nykyisissä standardeissa ja meluohjeissa. Tämä tutkimus osoitti, että oikein suoritetut psykoakustiset kokeet tarjoavat laadullista ja määrällistä tietoa subjektiivisesta häiritsevyydestä, ja että näiden tietojen perusteella voidaan määrittää objektiiviset mittarit, jotka tekisivät ohjearvoista tehokkaampia melun haitallisilta vaikutuksilta suojauduttaessa