Differential sound level meter

Small differences between relatively high sound pressure levels at two different microphone sites are measured by a device which provides electrical insertion voltages (pilot voltages) as a a means for continuously monitoring the gains of two acoustical channels. The difference between two pilot voltages is utilized to force the gain of one channel to track the other channel

Adjustment of interaural-time-difference analysis to sound level

To localize low-frequency sound sources in azimuth, the binaural system compares the timing of sound waves at the two ears with microsecond precision. A similarly high precision is also seen in the binaural processing of the envelopes of high-frequency complex sounds. Both for low- and high-frequency sounds, interaural time difference (ITD) acuity is to a large extent independent of sound level. The mechanisms underlying this level-invariant extraction of ITDs by the binaural system are, however, only poorly understood. We use high-frequency pip trains with asymmetric and dichotic pip envelopes in a combined psychophysical, electrophysiological, and modeling approach. Although the dichotic envelopes cannot be physically matched in terms of ITD, the match produced perceptually by humans is very reliable, and it depends systematically on the overall sound level. These data are reflected in neural responses from the gerbil lateral superior olive and lateral lemniscus. The results are predicted in an existing temporal-integration model extended with a level-dependent threshold criterion. These data provide a very sensitive quantification of how the peripheral temporal code is conditioned for binaural analysis

Heschl's gyrus is more sensitive to tone level than non-primary auditory cortex

Previous neuroimaging studies generally demonstrate a growth in the cortical response with an increase in sound level. However, the details of the shape and topographic location of such growth remain largely unknown. One limiting methodological factor has been the relatively sparse sampling of sound intensities. Additionally, most studies have either analysed the entire auditory cortex without differentiating primary and non-primary regions or have limited their analyses to Heschl's gyrus (HG). Here, we characterise the pattern of responses to a 300-Hz tone presented in 6-dB steps from 42 to 96 dB sound pressure level as a function of its sound level, within three anatomically defined auditory areas; the primary area, on HG, and two non-primary areas, consisting of a small area lateral to the axis of HG (the anterior lateral area, ALA) and the posterior part of auditory cortex (the planum temporale, PT). Extent and magnitude of auditory activation increased non-linearly with sound level. In HG, the extent and magnitude were more sensitive to increasing level than in ALA and PT. Thus, HG appears to have a larger involvement in sound-level processing than does ALA or PT

Handbook of aircraft noise metrics

Information is presented on 22 noise metrics that are associated with the measurement and prediction of the effects of aircraft noise. Some of the instantaneous frequency weighted sound level measures, such as A-weighted sound level, are used to provide multiple assessment of the aircraft noise level. Other multiple event metrics, such as day-night average sound level, were designed to relate sound levels measured over a period of time to subjective responses in an effort to determine compatible land uses and aid in community planning. The various measures are divided into: (1) instantaneous sound level metrics; (2) duration corrected single event metrics; (3) multiple event metrics; and (4) speech communication metrics. The scope of each measure is examined in terms of its: definition, purpose, background, relationship to other measures, calculation method, example, equipment, references, and standards

Identification of major noise donors, a sure way to abating noise

A Study was conducted to ascertain the specific noise emitted by presumed noisy environments. This was achieved by direct measurement of the noise with the use of an integrated sound level meter in which a built-in frequency filter or weighting network is incorporated. Ten (10) environments were selected in Ilorin and Akure towns in Nigeria, in which sixty (60) readings were taken at intervals of 30 seconds for 30minutes separately at each location. This amounted to an overall reading of six hundred (600) readings. The results show that the Lawn Mower emits noise with the highest Equivalent sound level

An underwater sound level meter

This thesis contains a description of the design and operation of an instrument for use as an underwater sound pressure level meter. Detailed descriptions are given of the techniques used to eliminate sources of error due to such limitations as thermal noise in the detection equipment and the lack of omnidirectionality of the hydrophone response. Data are presented comparing the thermal noise limit of both the hydrophone and the preamplifier to the equivalent noise level of Sea State zero. The use of the instrument is demonstrated by measuring the acoustic noise level in a low noise environment of an anechoic tank.Physic

Hydrophone sound level meter “Pontus”

Treball desenvolupat en el marc del programa "European Project Semester".The ocean is full of anthropogenic noise which can harm marine animals. The anthropogenic sounds can cause a threshold shift in their hearing sensibility, which can on its turn cause changes in their behavior. The aim of this project is to develop a portable hydrophone sound level meter that displays sound levels in real time. In addition, a warning signal will be displayed when a defined sound level is reached or surpassed. In order to achieve these goals, research was carried out. It was determined when sound levels and octaves become dangerous or deadly for the respective marine life. For the development process of the hydrophone sound level meter, it was important to determine requirements in order to make the device usable for this purpose. Based on the requirements, a selection of technical components and the design of the device was made. With the help of the necessary software, the measured values of a hydrophone can be displayed on the hydrophone sound level meter in an easily understandable way. In this report a final design of a hydrophone sound level meter is presented, which fulfils almost all requirements and objectives.Incomin

The effect of sound level on perception of reproduced soundscapes

The aim of this work was to investigate the perception of soundscape reproduced by an ambisonic reproduction system on a horizontal plane, how the experience of space affected the perception of soundscape reproduction, and how the sound level adjustment on soundscape reproduction affected the perception of soundscape compared with actual conditions. There were three experiments conducted: a soundwalk in situ in Manchester (United Kingdom) city centre, listening tests in Salford (United Kingdom), and listening tests in Bandung (Indonesia). The listening tests used material recorded from four locations on the soundwalk route in Manchester. The Salford listening tests were performed at the in-situ measured sound level, and the participants were asked to adjust the sound level to the level that represents actual locations. The listening test in Bandung was conducted to understand the effect of participants who never come to the actual location to the perception of soundscape and the sound level adjustment. The listening tests in Bandung were conducted at the in situ sound level, at 9.5 dB below the in situ sound level (based on the preference sound level from the experiment in Salford), and the participants were also requested to adjust the sound level to the level that represents the actual space (to examine the consistency with the experiment in Salford). In each case, soundscape perception was measured on 19 semantic differential scales. Analysis of the semantic differential results showed that the ambisonic reproduction produced a similar subjective experience to the in situ soundwalk when the reproduction sound level was 9.5 dB lower than the actual sound level in situ. Reproduction at the actual sound level in situ produced a different dimensional space. The study shows that the sound level adjustment of soundscape reproduction in laboratory experiment produces more ecologically valid results compared to the reproduction at the actual sound level in situ

Noise measurements for various configurations of a model of a mixer nozzle externally blown flap system

Noise data were taken for variations to a large scale model of an externally blown flap lift augmentation system. The variations included two different mixer nozzles (7 and 8 lobes), two different wing models (2 and 3 flaps), and different lateral distances between the wing chord line and the nozzle centerline. When the seven lobe was used with the trailing flap in the 60 deg position, increasing the wing to nozzle distance had no effect on the sound level. When the eight lobe nozzle was used there was a decrease in sound level. With the 20 deg flap setting the noise level decreased when the distance was increased using either nozzle