Acoustic Absorbers and Diffusers

Cox, Trevor J.; D’Antonio, Peter

doi:10.4324/9781482266412

Cited by 154 publications

(45 citation statements)

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“…Lastly, we note that the ventromedial surface of the crests of Platanista is highly rugose, a characteristic that would also influence the reflective properties of the crests. More complex surfaces provide a relatively larger surface for sound to interact with, and thus function better as sound absorbers and sound diffusers than as sound reflectors [ 72 ]. However, if the interface between the air sac system and the soft tissue acts to reflect sound, then the surface of this bone may not be important in determining the reflective properties of this system.…”

Section: Resultsmentioning

confidence: 99%

A new fossil dolphinDilophodelphis fordyceiprovides insight into the evolution of supraorbital crests in Platanistoidea (Mammalia, Cetacea)

2017

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Many odontocete groups have developed enlarged facial crests, although these crests differ in topography, composition and function. The most elaborate crests occur in the South Asian river dolphin (Platanista gangetica), in which they rise dorsally as delicate, pneumatized wings anterior of the facial bones. Their position wrapping around the melon suggests their involvement in sound propagation for echolocation. To better understand the origin of crests in this lineage, we examined facial crests among fossil and living Platanistoidea, including a new taxon, Dilophodelphis fordycei, nov. gen. and sp., described herein, from the Early Miocene Astoria Formation of Oregon, USA. We measured the physical extent and thickness of platanistoid crests, categorized their relative position and used computed tomography scans to examine their internal morphology and relative bone density. Integrating these traits in a phylogenetic context, we determined that the onset of crest elaboration or enlargement and the evolution of crest pneumatization among the platanistoids were separate events, with crest enlargement beginning in the Oligocene. However, we find no evidence for pneumatization until possibly the Early Miocene, although certainly by the Middle Miocene. Such an evolutionary context, including data from the fossil record, should inform modelling efforts that seek to understand the diversity of sound generation morphology in Odontoceti.

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Section: Resultsmentioning

confidence: 99%

A new fossil dolphinDilophodelphis fordyceiprovides insight into the evolution of supraorbital crests in Platanistoidea (Mammalia, Cetacea)

2017

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“…Reverberation time could be manipulated through placing acoustic materials on the ceiling or wall of a room. Currently, both Sabin equation (equation (55)) and Eyring equation (equation (56)) are widely used to calculate the reverberation time of a room [8,109]. The expressions of these two models are shown as follows where V is room volume (m 3 ), S is room surface area (m 2 ) and α¯ is the average diffuse-field sound absorption coefficients of the room.…”

Section: Applications Of Airflow Resistancementioning

confidence: 99%

Airflow resistance of acoustical fibrous materials: Measurements, calculations and applications

Tang

Xiong

2018

Journal of Industrial Textiles

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The acoustic performance of fibrous materials is mainly determined by its airflow resistance, and it is a parameter of the resistance that the airflow meets through the materials. This paper has summarized the recent advances on the measurements, calculations and applications of airflow resistance. Firstly, different methods for airflow resistance measurements are presented, mainly including the direct airflow method, alternating airflow method and acoustical method. We have summarized the development history, current status and industrial applications of these methods. Secondly, this paper has summarized the models of calculating airflow resistance. Most of these empirical models are based on the characteristic parameters of fibrous materials, for instance bulk density, fiber diameter, porosity and thickness. Thirdly, this review has gathered the applications of airflow resistance in sound absorption and noise control. It is a crucial parameter in the prediction of both normal incidence sound absorption and reverberation chamber sound absorption. In conclusion, this review has concluded with some perspectives for the measurements, calculations and applications of airflow resistance.

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“…Further, absorption coefficients of interior finishing materials used in the examined dwelling units were obtained from the literature. 22 Table 3 displays the main input data of the simulation.…”

Section: Acoustic Conditions Pertaining To Alarm-device Audibilitymentioning

confidence: 99%

Sound attenuation and audibility of fire alarm signal in Korean residential apartment buildings: A case study

Lee¹,

Kim

2017

Indoor and Built Environment

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With a view to preventing casualties due to fire outbreaks in residential buildings, we investigated the sound attenuation of audible fire-alarm signals in Korean residential apartment buildings and determine an acoustic condition for enhancing the audibility of such signals. Two sets of field measurements were performed, along with theoretical predictions using sound analysis software. In the first set of measurements, in 17 dwelling units, the standardized alarm sound level requirement of 75 dBA could not be achieved in bedrooms with existing alarm devices. In the second set of measurements, with an additional five dwelling units, both the sound attenuation according to the distance between sound sources and bedrooms and the sound insulation performance of bedroom doors were examined. The sound attenuation levels were increased by 0.72 ( R2 = 0.7982) and 0.48 ( R2 = 0.3001) dB m−1 under open- and closed-door conditions, respectively. Further, the bedroom-door sound insulation performance was in the 18- to 23-dB range. Consequently, we have demonstrated that the sound power of a general residential fire alarm must be 98–107.9 dB, depending on the dwelling-unit size and floor-plan type, in order to achieve a bedroom audibility level of 75 dBA.

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Acoustic Absorbers and Diffusers

Cited by 154 publications

References 0 publications

A new fossil dolphinDilophodelphis fordyceiprovides insight into the evolution of supraorbital crests in Platanistoidea (Mammalia, Cetacea)

A new fossil dolphinDilophodelphis fordyceiprovides insight into the evolution of supraorbital crests in Platanistoidea (Mammalia, Cetacea)

Airflow resistance of acoustical fibrous materials: Measurements, calculations and applications

Sound attenuation and audibility of fire alarm signal in Korean residential apartment buildings: A case study

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