SciCombinator

Discover the most talked about and latest scientific content & concepts.

Concept: Sound pressure

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The current research examined the relationship between hierarchy and vocal acoustic cues. Using Brunswik’s lens model as a framework, we explored how hierarchical rank influences the acoustic properties of a speaker’s voice and how these hierarchy-based acoustic cues affect perceivers' inferences of a speaker’s rank. By using objective measurements of speakers' acoustic cues and controlling for baseline cue levels, we were able to precisely capture the relationship between acoustic cues and hierarchical rank, as well as the covariation among the cues. In Experiment 1, analyses controlling for speakers' baseline cue levels found that the voices of individuals in the high-rank condition were higher in pitch and loudness variability but lower in pitch variability, compared with the voices of individuals in the low-rank condition. In Experiment 2, perceivers used higher pitch, greater loudness, and greater loudness variability to make accurate inferences of speakers' hierarchical rank. These experiments demonstrate that acoustic cues are systematically used to reflect and detect hierarchy.

Concepts: Experiment, Hierarchy, Loudspeaker, Greek loanwords, Sound pressure, Sound, Human voice

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Jumping spiders (Salticidae) are famous for their visually driven behaviors [1]. Here, however, we present behavioral and neurophysiological evidence that these animals also perceive and respond to airborne acoustic stimuli, even when the distance between the animal and the sound source is relatively large (∼3 m) and with stimulus amplitudes at the position of the spider of ∼65 dB sound pressure level (SPL). Behavioral experiments with the jumping spider Phidippus audax reveal that these animals respond to low-frequency sounds (80 Hz; 65 dB SPL) by freezing-a common anti-predatory behavior characteristic of an acoustic startle response. Neurophysiological recordings from auditory-sensitive neural units in the brains of these jumping spiders showed responses to low-frequency tones (80 Hz at ∼65 dB SPL)-recordings that also represent the first record of acoustically responsive neural units in the jumping spider brain. Responses persisted even when the distances between spider and stimulus source exceeded 3 m and under anechoic conditions. Thus, these spiders appear able to detect airborne sound at distances in the acoustic far-field region, beyond the near-field range often thought to bound acoustic perception in arthropods that lack tympanic ears (e.g., spiders) [2]. Furthermore, direct mechanical stimulation of hairs on the patella of the foreleg was sufficient to generate responses in neural units that also responded to airborne acoustic stimuli-evidence that these hairs likely play a role in the detection of acoustic cues. We suggest that these auditory responses enable the detection of predators and facilitate an acoustic startle response. VIDEO ABSTRACT.

Concepts: Salticidae, Acoustics, Sound pressure, Sound, Jumping spider, Psychology, Spider, Arthropod

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Sound produced by fish spawning aggregations (FSAs) permits the use of passive acoustic methods to identify the timing and location of spawning. However, difficulties in relating sound levels to abundance have impeded the use of passive acoustics to conduct quantitative assessments of biomass. Here we show that models of measured fish sound production versus independently measured fish density can be generated to estimate abundance and biomass from sound levels at FSAs. We compared sound levels produced by spawning Gulf Corvina (Cynoscion othonopterus) with simultaneous measurements of density from active acoustic surveys in the Colorado River Delta, Mexico. During the formation of FSAs, we estimated peak abundance at 1.53 to 1.55 million fish, which equated to a biomass of 2,133 to 2,145 metric tons. Sound levels ranged from 0.02 to 12,738 Pa(2), with larger measurements observed on outgoing tides. The relationship between sound levels and densities was variable across the duration of surveys but stabilized during the peak spawning period after high tide to produce a linear relationship. Our results support the use of active acoustic methods to estimate density, abundance, and biomass of fish at FSAs; using appropriately scaled empirical relationships, sound levels can be used to infer these estimates.

Concepts: Cynoscion, Sound pressure, Approximation, Tide, Estimation, Colorado River, Sound, Acoustics

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Biological sounds produced on coral reefs may provide settlement cues to marine larvae. Sound fields are composed of pressure and particle motion, which is the back and forth movement of acoustic particles. Particle motion (i.e., not pressure) is the relevant acoustic stimulus for many, if not most, marine animals. However, there have been no field measurements of reef particle motion. To address this deficiency, both pressure and particle motion were recorded at a range of distances from one Hawaiian coral reef at dawn and mid-morning on three separate days. Sound pressure attenuated with distance from the reef at dawn. Similar trends were apparent for particle velocity but with considerable variability. In general, average sound levels were low and perhaps too faint to be used as an orientation cue except very close to the reef. However, individual transient sounds that exceeded the mean values, sometimes by up to an order of magnitude, might be detectable far from the reef, depending on the hearing abilities of the larva. If sound is not being used as a long-range cue, it might still be useful for habitat selection or other biological activities within a reef.

Concepts: Particle displacement, Marine biology, Coral, Sound power, Acoustics, Sound, Sound pressure, Coral reef

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Propagation patterns of animal acoustic signals provide insights into the evolution of signal design to convey signaler’s information to potential recipients. However, propagation properties of vertebrate calls have been rarely studied using natural calls from individuals; instead playback calls broadcast through loudspeakers have been used extensively, a procedure that may involve acoustical and physical features differing from natural sounds. Measurements of the transmission characteristics of natural advertisement calls, which are simple tonal sounds, of the Iberian midwife toad, Alytes cisternasii, were carried out, and the results were compared with previously published results broadcasting recorded calls of the same species. Measurements of sound pressure level (SPL) of calls from individual male A. cisternasii revealed that the call amplitude decreases at distances of 1-8 m from the source at rates averaging 1-5 dB above spherical transmission loss in an omni-directional pattern. A comparison between SPLs of natural calls in the current study and of playback calls from a previous study showed that patterns of propagation did not differ in average values, but variance was significantly higher for natural calls. Results suggest that using broadcast signals for transmission experiments may result in a simplification of the conditions in which actual animals communicate in nature.

Concepts: Microphone, Level, Bioacoustics, Broadcasting, Sound pressure, Average, Acoustics, Sound

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We investigated the contribution of the middle ear to the physiological response to bone conduction stimuli in chinchilla. We measured intracochlear sound pressure in response to air conduction (AC) and bone conduction (BC) stimuli before and after interruption of the ossicular chain at the incudo-stapedial joint. Interruption of the chain effectively decouples the external and middle ear from the inner ear and significantly reduces the contributions of the outer ear and middle ear to the bone conduction response. With AC stimulation, both the scala vestibuli Psv and scala tympani Pst sound pressures drop by 30 to 40 dB after the interruption. In BC stimulation, Psv decreases after interruption by about 10 to 20 dB, but Pst is little affected. This difference in the sensitivity of the BC induced Psv and Pst to ossicular interruption is not consistent with a BC response to ossicular motion, but instead suggests a significant contribution of an inner-ear drive (e.g. cochlear fluid inertia or compressibility) to the BC response.

Concepts: Sound, Microphone, Scala vestibuli, Sound pressure, Ear, Inner ear, Cochlea, Auditory system

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There is currently no ASTM method for field measurement of the acoustical noise isolation specific to doors. Measurement of the overall noise reduction of the composite wall/door assembly or the Apparent Sound Transmission Class of the door can be attempted using the methods in ASTM E336, but these methods are not well suited to measuring doors. Doors typically have poorly defined source and receiving rooms, such as long and narrow corridors, stairwells, or outdoor spaces, which often do not meet the room requirements of ASTM E336. The sound fields are rarely diffuse, and the measurement locations are not well defined in the ASTM standard. An alternative insertion loss method (i.e., a comparison of the sound pressure levels with the door open and closed) was developed by MJM Acoustical Consultants (Michel Morin, “Research project on the noise isolation provided by access doors in multi-dwelling buildings,” 1993), and a draft ASTM standard has been developed based on this method. A laboratory testing program has been designed evaluate the proposed method and investigate variations in the test method. The results of the laboratory testing program are presented.

Concepts: Architectural acoustics, Standard, Sound pressure, Metrology, Sound, Acoustics, Measurement, Test method

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OBJECTIVES: To investigate listening habits and hearing risks associated with the use of personal listening devices among urban high school students in Malaysia. STUDY DESIGN: Cross-sectional, descriptive study. METHODS: In total, 177 personal listening device users (13-16 years old) were interviewed to elicit their listening habits (e.g. listening duration, volume setting) and symptoms of hearing loss. Their listening levels were also determined by asking them to set their usual listening volume on an Apple iPod TM playing a pre-selected song. The iPod’s sound output was measured with an artificial ear connected to a sound level meter. Subjects also underwent pure tone audiometry to ascertain their hearing thresholds at standard frequencies (0.5-8 kHz) and extended high frequencies (9-16 kHz). RESULTS: The mean measured listening level and listening duration for all subjects were 72.2 dBA and 1.2 h/day, respectively. Their self-reported listening levels were highly correlated with the measured levels (P < 0.001). Subjects who listened at higher volumes also tend to listen for longer durations (P = 0.012). Male subjects listened at a significantly higher volume than female subjects (P = 0.008). When sound exposure levels were compared with the recommended occupational noise exposure limit, 4.5% of subjects were found to be listening at levels which require mandatory hearing protection in the occupational setting. Hearing loss (≥25 dB hearing level at one or more standard test frequencies) was detected in 7.3% of subjects. Subjects' sound exposure levels from the devices were positively correlated with their hearing thresholds at two of the extended high frequencies (11.2 and 14 kHz), which could indicate an early stage of noise-induced hearing loss. CONCLUSIONS: Although the average high school student listened at safe levels, a small percentage of listeners were exposed to harmful sound levels. Preventive measures are needed to avoid permanent hearing damage in high-risk listeners.

Concepts: Noise pollution, Tinnitus, High school, Hearing, Hearing impairment, Sound, Sound pressure, Audiogram

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To determine if sound-activated noise meters providing direct audit and visual feedback can reduce sound levels in a level 3 neonatal intensive care unit (NICU).

Concepts: Electrochemistry, Sound pressure, Pediatrics, Neonatal intensive care unit, Intensive care medicine

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Objective: To determine noise intensity during middle-ear aspiration in order to evaluate whether levels can be potentially harmful. Methods: In this prospective, observational study, middle-ear effusion was aspirated following myringotomy using a suction instrument with a probe tube microphone. Sound pressure levels and duration were measured, and frequency domain analysis was performed. Results: Forty-four ears were analysed, consisting of 20 with mucoid effusion, 11 with serous effusion and 13 with no effusion. Maximum peak sound intensity ranged from 84 to 157 dB. Half of the ears (50 per cent) were exposed to greater than 140 dB; of these, 82 per cent were exposed for longer than 0.2 ms (range, 0.05-14 ms). There was no significant difference in sound pressure level between ears with mucoid and serous effusion; however, ears with mucoid effusion required longer suction times (p < 0.0030). In addition, peak intensity was greater for ears with mucoid effusion versus those with serous or no effusion (p < 0.0001). Conclusion: Middle-ear aspiration during myringotomy caused noise levels within a potentially harmful range.

Concepts: Ear, Particle displacement, Sound power, Sound intensity, Level, Microphone, Sound, Sound pressure