Aircraft interior acoustics - background noise contamination

2021 ◽  
Vol 263 (5) ◽  
pp. 1606-1619
Author(s):  
Ramana Kappagantu ◽  
Manuel Etchessahar ◽  
Edgar Matas ◽  
Koen Vansant
Keyword(s):  
High Frequency ◽  
Background Noise ◽  
Noise Source ◽  
Operating Conditions ◽  
Low Frequencies ◽  
Acoustic Design ◽  
Points Of Interest ◽  
Transmission Index ◽  
Speech Transmission ◽  
Noise Contamination

Aircraft interior noise is an important factor to be considered for cabin comfort. In a cruising condition this noise source is mostly broadband in nature and is coming from the exterior, primarily the turbulent boundary layer (TBL) of the flow around the moving aircraft. Capturing this noise to a high frequency is critical for designing the sound packaging. Also, this becomes important in the design of public announcement (PA) system for the aircraft cabin, i.e. the correct placement of speakers. One of the metrics used for this acoustic design is speech transmission index. Deterministic techniques like finite or boundary element techniques for low frequencies and ray tracing method to reach higher frequencies are better suited for getting the narrow band responses. On the other hand, to characterize the background noise due to the TBL loads, statistical energy analysis (SEA) route is pursued. In this paper the authors combine different techniques to capture the background noise and use them with PA sources and eventually capture the sound perceived at points of interest. The articulation metrics are compared for different operating conditions of the aircraft. In the presentation attempts will be made to play the auralized sounds.

Mapping speech transmission index (STI) and background noise in university classrooms

2017 ◽  
Vol 141 (5) ◽  
pp. 3481-3481
Author(s):  
Andrew Hulva ◽  
Michael Ermann ◽  
Jeffrey Rynes ◽  
Randall J. Rehfuss ◽  
Aaron Kanapesky ◽  
...  
Keyword(s):  
Background Noise ◽  
Transmission Index ◽  
Speech Transmission ◽  
University Classrooms

Further Validation of the Speech Transmission Index (STI)

1987 ◽  
Vol 30 (3) ◽  
pp. 403-410 ◽  
Author(s):  
Larry E. Humes ◽  
Stephen Boney ◽  
Faith Loven
Keyword(s):  
Speech Recognition ◽  
Background Noise ◽  
Recognition Task ◽  
Sound Field ◽  
Normal Hearing ◽  
Noise Levels ◽  
Transmission Index ◽  
Speech Transmission ◽  
Binaural Listening ◽  
Prospective Analyses

The present article further evaluates the accuracy of speech-recognition predictions made according to two forms of the Speech Transmission Index (STI) for normal-hearing listeners. The first portion of this article describes the application of the modified Speech Transmission Index (mSTI) to an extensive set of speech-recognition data. Performance of normal-hearing listeners on a nonsense-syllable recognition task in 216 conditions involving different speech levels, background noise levels, reverberation times and filter passbands was found to be monotonically related to the mSTI. The second portion of this article describes a retrospective and prospective analysis of an extended sound-field version of the STI, referred to here as STI x . This extended STI considers many of the variables relevant to sound-field speech recognition, some of which are not incorporated in the mSTI. These variables include: (a) reverberation time; (b) speech level; (e) noise level; (d) talker-to-listener distance; (e) directivity of the speech source; and (f) directivity of the listener (eg., monaural vs. binaural listening). For both the retrospective and prospective analyses, speech-recognition was found to vary monotonically with STI x .

scholarly journals Changes on Speech Transmission Characteristics by Types of Mask

2020 ◽  
Vol 16 (4) ◽  
pp. 295-304
Author(s):  
Jeongho Jeong ◽  
Mina Kim ◽  
Youngsun Kim
Keyword(s):  
High Frequency ◽  
Face Mask ◽  
Octave Band ◽  
Transmission Characteristics ◽  
High Frequencies ◽  
Working Environments ◽  
Transmission Index ◽  
Speech Transmission ◽  
Long Time ◽  
The Face

Purpose: Given the increased levels of fine and ultrafine dust, as well as the spread of COVID-19, current opinion is that most people will wear a face mask such a KF94 mask for a long time. To test speech transmission through the face masks, various types of masks including dust masks available in the market at the time of the study were tested under laboratory conditions.Methods: Fourteen types of masks worn on a head and torso simulator (HATS) and test signals were played on a speaker installed in the mouse position of the HATS. Speech Transmission Index (STI) and the speech level in the octave band were measured at distances of 1 m and 2 m.Results: STI at a distance of 2 m was decreased to 3.4-5.7% and speech levels in the octave band at 4 kHz or higher were also decreased when wearing disposable masks and a cotton mask. KF80 and KF94 masks showed decreased STI similar to those of disposable masks; however, a decrease in the speech level was observed at the octave bands of above 2 kHz. Dust masks and single-cartridge half-face respirators showed approximately 11.2% and 33.7% to 39.3% decreases in STI levels, respectively.Conclusion: When wearing masks, STI and the speech level was decreased in the high-frequency bands. However, speech level differences at high frequencies may be related to the increased voice level of the speaker and the understanding of consonants with the masks for several hours in living and working environments.

Impact of Partition types on Architecture design studios acoustical environment

2021 ◽  
Vol 263 (1) ◽  
pp. 5847-5857
Author(s):  
Hany Hossam Eldien ◽  
Umaru Bongwirnso
Keyword(s):  
Background Noise ◽  
Speech Intelligibility ◽  
Architecture Design ◽  
Front Side ◽  
Open Spaces ◽  
Transmission Index ◽  
Speech Transmission ◽  
Open Plan ◽  
High Level ◽  
Two Sides

Working in Architecture design studios environment requires various activities. Interaction, communication and meetings could affect the speech intelligibility and the speech privacy conditions. Students Areas with a more silent environment are needed with a minimized level of distraction from surrounding activities, while teamwork and discussion areas with a high level of interaction need a good speech intelligibility. One of the more important elements which can improve the open spaces acoustical conditions is the partitions between workstations.The main purpose of this work is to evaluate the acoustical performance of four partitions types in open plan offices; 1.10m two sides partition height, 1,50m front side partitions, 1,50m one side partitions and 1.50 two sides partitions. This Study was conducted in the College of Architecture, Imam Abdulrhman Bin Faisal University, KSA. Based on ISO 3382-3, Speech Transmission Index, STI in the nearest workstation, Distraction distance rD, privacy distance rP, A-weighted background noise level L,A,B and A-weighted SPL of speech at 4 metres L,A,S,4m have been measured. It was found that the best results can be obtained by 1.50m front side and 1.50m two sides partitions.

scholarly journals Acoustic quality assessment in a classroom through simulations and measurements

2021 ◽  
Vol 9 (72) ◽  
Author(s):  
Eriberto Oliveira do Nascimento ◽  
Paulo Henrique Trombetta Zannin
Keyword(s):  
Background Noise ◽  
Speech Intelligibility ◽  
Reverberation Time ◽  
Vocal Health ◽  
Quality Requirements ◽  
Transmission Index ◽  
Speech Transmission ◽  
Acoustic Quality ◽  
Acoustic Comfort ◽  
Minimum Requirements

The acoustic quality in a classroom directly impacts the educational relationship between the student and the teacher, reducing speech intelligibility. In addition, inadequate acoustic comfort burdens the vocal health of teachers. This study evaluated a classroom at the Federal University of Paraná, Campus Centro Politécnico, to verify its acoustic quality. The measurements of the acoustics descriptors: Reverberation Time (RT), Definition (D50), Central Time (Ts), Early Decay Time (EDT) were performed according to the ISO 3382-2 standard, concerning Noise Curves (NC) and Background Noise (BGN) these were evaluated by the  NBR 10152 and S12.2 standards. The Speech Transmission Index (STI) was measured according to IEC 60268-16 and evaluated according to ISO 9921. The useful-detrimental ratio (U50) and the other descriptors were simulated in the ODEON software version 11. Thus, the results showed that the evaluated room did not meet the minimum requirements in terms of acoustic quality, for the descriptors RT, STI, Ts, D50, RF, and NC. Simultaneously, the RT and STI were also outside the limits established by the German and Finnish standards. Therefore, it is concluded that the evaluated classroom did not reach the minimum acoustic quality requirements.

Comparisons of downhole geophones and hydrophones

Geophysics ◽  
1992 ◽  
Vol 57 (6) ◽  
pp. 841-847 ◽  
Author(s):  
Christine E. Krohn ◽  
S. T. Chen
Keyword(s):  
High Frequency ◽  
Background Noise ◽  
Low Frequency ◽  
Measured Signal ◽  
Coherent Noise ◽  
Low Frequencies ◽  
Prototype Tool ◽  
The Difference ◽  
Borehole Seismic ◽  
Seismic Applications

Receiver tests were conducted to compare the responses of downhole geophones and hydrophones. Commercial receiver tools use a maximum of eight geophone levels; however, we use hydrophones because we can record 48 levels simultaneously. For frequencies above 300 Hz, signal‐to‐background‐noise ratios for hydrophones and geophones in a prototype tool were comparable. (This prototype tool is a lightweight, large‐clamping‐force device that can record higher frequencies than commercial geophone tools.) For frequencies below 300 Hz, signal‐to‐noise ratios were greater for the geophones than for the hydrophones. A commercial geophone tool had lower low‐frequency signal‐to‐background‐noise ratios than the prototype tool, but greater than those of the hydrophones. Further analysis was performed to determine why the signal‐to‐background‐noise ratios for geophones were greater than those for hydrophones at low frequencies. The measured signal level for a hydrophone was 2.4 times that for a geophone, compared with a theoretical prediction of 1.8. Thus, the signal levels do not explain the difference in signal‐to‐background‐noise ratios. The low‐frequency background noise was attributed to coherent noise in the form of tube waves, a noise type to which hydrophones are much more susceptible than are geophones. Thus, the low signal‐to‐background‐noise ratios at frequencies below 300 Hz for hydrophones resulted from ambient noise propagating as tube waves in the borehole. The high‐frequency background noise was attributed to random seismic noise in the environment and not to instrument noise. These results show that hydrophones, which do not need to be clamped to the borehole wall, are preferable to geophones for high‐frequency borehole seismic applications using first arrivals. Geophones are preferable to hydrophones for borehole seismic applications using reflector arrivals, because these later‐arriving events are obscured by source‐generated tube waves in hydrophone data. Development of a method to reduce both the source‐generated and ambient tube‐wave noise detected by hydrophones would result in high‐quality borehole seismic data at a greatly reduced cost.

scholarly journals A Study of the Acoustics and Speech Intelligibility Quality of Mosques in Malaysia

2014 ◽  
Vol 564 ◽  
pp. 129-134
Author(s):  
Abdul Hakim Abdullah ◽  
Zamir A. Zulkefli
Keyword(s):  
Background Noise ◽  
Speech Intelligibility ◽  
Prediction Models ◽  
Signal To Noise Ratio ◽  
Distribution Patterns ◽  
Speech Quality ◽  
Transmission Index ◽  
Speech Transmission ◽  
Rapid Transmission

This study presents the assessment of the quality of speech intelligibility of two Malaysian mosques and the results are used to develop a set of general acoustical guidelines to be used in the design of a mosque. Two mosques were selected for the research: Masjid UPM and the Masjid Jamek. The objective of the research is to enable the comparison of the acoustics and speech intelligibility between the mosques as function of the size, volume, occupancy and other parameters of the main prayer hall on the acoustic and speech intelligibility of the respective mosques. The reverberation time (RT60), speech level (SL), background noise (BN), signal-to-noise ratio (S/N ratio) were determined and are used to develop the speech transmission index (STI) and rapid transmission index (RASTI) prediction models for both mosques. It was observed from the results that the RT60, STI and RASTI values shows better performance over number of occupancy for both mosques. Furthermore, the BN and SL results were visualized using the spatial distribution patterns (SDP) of the main hall. The results of the analysis show that the overall acoustic and speech quality of Masjid Jamek is better when compared to the overall acoustic and speech quality of Masjid UPM. These results are then used to develop a set of design recommendations to ensure adequate speech intelligibility quality a mosque.

scholarly journals Evidence for hearing loss in amblyopsid cavefishes

2013 ◽  
Vol 9 (3) ◽  
pp. 20130104 ◽  
Author(s):  
Matthew L. Niemiller ◽  
Dennis M. Higgs ◽  
Daphne Soares
Keyword(s):  
Hearing Loss ◽  
High Frequency ◽  
Background Noise ◽  
Ambient Noise ◽  
Constant Darkness ◽  
Low Frequencies ◽  
The Family ◽  
Sensory Modalities ◽  
Hearing Range ◽  
Cell Densities

The constant darkness of caves and other subterranean habitats imposes sensory constraints that offer a unique opportunity to examine evolution of sensory modalities. Hearing in cavefishes has not been well explored, and here we show that cavefishes in the family Amblyopsidae are not only blind but have also lost a significant portion of their hearing range. Our results showed that cave and surface amblyopsids shared the same audiogram profile at low frequencies but only surface amblyopsids were able to hear frequencies higher than 800 Hz and up to 2 kHz. We measured ambient noise in aquatic cave and surface habitats and found high intensity peaks near 1 kHz for streams underground, suggesting no adaptive advantage in hearing in those frequencies. In addition, cave amblyopsids had lower hair cell densities compared with their surface relative. These traits may have evolved in response to the loud high-frequency background noise found in subterranean pools and streams. This study represents the first report of auditory regression in a subterranean organism.

scholarly journals Earless toads sense low frequencies but miss the high notes

2017 ◽  
Vol 284 (1864) ◽  
pp. 20171670 ◽  
Author(s):  
Molly C. Womack ◽  
Jakob Christensen-Dalsgaard ◽  
Luis A. Coloma ◽  
Juan C. Chaparro ◽  
Kim L. Hoke
Keyword(s):  
High Frequency ◽  
Species Differences ◽  
Low Frequency ◽  
Auditory Brainstem ◽  
Low Frequencies ◽  
Hearing Sensitivity ◽  
Sensory Pathways ◽  
Airborne Sound ◽  
Vibrational Sensitivity ◽  
Species Specific

Sensory losses or reductions are frequently attributed to relaxed selection. However, anuran species have lost tympanic middle ears many times, despite anurans' use of acoustic communication and the benefit of middle ears for hearing airborne sound. Here we determine whether pre-existing alternative sensory pathways enable anurans lacking tympanic middle ears (termed earless anurans) to hear airborne sound as well as eared species or to better sense vibrations in the environment. We used auditory brainstem recordings to compare hearing and vibrational sensitivity among 10 species (six eared, four earless) within the Neotropical true toad family (Bufonidae). We found that species lacking middle ears are less sensitive to high-frequency sounds, however, low-frequency hearing and vibrational sensitivity are equivalent between eared and earless species. Furthermore, extratympanic hearing sensitivity varies among earless species, highlighting potential species differences in extratympanic hearing mechanisms. We argue that ancestral bufonids may have sufficient extratympanic hearing and vibrational sensitivity such that earless lineages tolerated the loss of high frequency hearing sensitivity by adopting species-specific behavioural strategies to detect conspecifics, predators and prey.

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