SPL Values Research Articles

Quantitative Assessments of the Liquefaction Hazard of Soils considering Possible Strong Earthquakes in Seismically Active Regions of Russia

Introduction The seismogenic liquefaction of the soil poses a great hazard to society and the environment. Therefore, it is actively studied in many countries. In Russian engineering and seismological practice, this area is not sufficiently developed. The deterministic approach still prevails in Russian research on this topic. More modern probabilistic estimates are very rare. Methods This paper describes examples of both deterministic and probabilistic assessments of the seismogenic liquefaction hazard performed in certain areas of the Russian territory with different seismogeological conditions. Deterministic estimates were made using the Iwasaki-Seed-Finn methods and their modifications. Probability distribution functions of a random variable, the “seismic potential of liquefaction” (SPL), were developed for probabilistic estimates. These functions are regional in nature and take into account two types of uncertainties. The first is the uncertainty in achieving “critical” values by the SPL value in the event of potentially dangerous earthquake sources for a given location. The second is the uncertainty in the very occurrence of these sources in a given place for a given period of time. The “critical” SPL values are determined by the strength properties of the site soils. All estimates are based on multivariate calculations using various models of strong ground motions and seismicity. In all cases, the probability of liquefaction of water-saturated sandy and sandy-loam deposits was estimated which were found near the seabed and at depths of up to 80 m in the waters of Pogibi cape (the coast of Sakhalin island), in the districts of Sochi and Novorossiysk, as well as in land conditions (Stavropol, Krasnodar). Results The results of the research made it possible to correctly (at the quantitative level) take into account this component of the seismic hazard of the studied territories. Conclusion The variants of practical use of the obtained data are offered. An assessment of the possibilities and limitations of the developed methodology is made, and ways to improve it are outlined.

The spontaneous activities of the multiple demand network are related to individual differences in indirect replies comprehension

This study aims to investigate the brain networks engaged in the comprehension of indirect language, as well as the individual difference in this capacity. Specially, we aim to determine whether the difference is solely influenced by the difference in individuals’ default network (DN)/language network or whether it also relies on the networks associated with processing of complex cognitive tasks, particularly the multiple demand network (MDN). Conversational indirectness scale (CIS) scores in the interpretation dimension were used as a behavioral indicator of the indirect comprehension tendency. Reading time difference between indirect replies and direct replies collected through a self-paced reading experiment was deemed as a behavioral indicator of comprehension speed of indirect replies comprehension. The two behavioral indicators were combined with resting-state functional magnetic resonance imaging (rs-fMRI). The behaviour-rfMRI analysis showed that ALFF value of right SPL and the functional connectivity (FC) between the right SPL and right IPL/SMA/ITG/Precuneus/bilateral IFG were positively correlated with the interpretation dimension of CIS scores. In addition, the ALFF value of right fusiform gyrus, the FC between the right fusiform gyrus and right precuneus, and the FCs between right SPL and right IPL/Precuneus/IFG were negatively correlated with indirect replies comprehension speed. Overlapping of these regions with large-scale brain network revealed that the right SPL was mainly located in the MDN, and the right fusiform gyrus was mainly located in the language network. Additionally, the areas showing functional connectivity with these regions were primarily located in the MDN, with a smaller subset located in the DN. Our findings suggest that the ability of individuals to actively and rapidly acquire indirect meaning relies not only on the support of the DN and the language network, but also requires collective support from the MDN.

Numerical Investigation of the Flow Structure and Acoustical Noise in a Suppressor

The noise created when a firearm is fired has a lot of adverse effects on humans and the environment, so analyzing and attenuating this noise is essential. This study aimed to examine propellant flow and the sound generated by this flow using a hybrid computational fluid dynamics and computational aeroacoustics method. The compatibility of this numerical study was also validated by comparing it with the experimental result. The impact of critical parameters, such as the shape and number of baffles of the suppressor, was studied. Finally, the overpressure and acoustics results of different suppressors were compared with each other and with the unsuppressed condition. According to the result, the suppressor with curved baffles shows a better performance. When the exit pressure at the tip of suppressor compared to the initial inlet pressure to the suppressor the percentage drop in overpressure was 76.01%, 78.79% and 81.3% for the suppressor with one, three and five curved baffles, respectively. For condition without suppressor, 169.49[Formula: see text]dB of SPL was recorded. When using a suppressor without a baffle, this value was reduced to 162.13[Formula: see text]dB. For the suppressor with one, three and five curved baffles, the SPL value was 160.234[Formula: see text]dB, 159.43[Formula: see text]dB and 158.11[Formula: see text]dB, respectively. Generally, this study shows that the suppressor’s efficiency is directly proportional to its shape and number of baffles.

Auralization and Visualization for Infrastructure Planning in the Joint Project "EAV-Infra"

Within the joint research project "Real-time Calculation, Auralization and Visualization of Sound Propagation and Noise Protection Measures for Infrastructure Projects" (EAV-Infra), funded by the Federal Ministry for Economic Affairs, the potentials of digital infrastructure planning based on Building Information Modeling (BIM) and the auralization of different states of planning will be combined. In this contribution, the objectives of the project will be presented with particular focus on the auralization. Currently, the effectiveness of noise mitigation measures like acoustic barriers or rail dampers is evaluated and communicated mostly by means of SPL values. Through auralization, a more vivid impression of different states of planning can be given during the whole planning process. In EAV-Infra, the auralization will be based on audio data of partial sound sources taken from real train passings. The data will be collected at various sites using a newly developed MEMS microphone array. To achieve a realistic hearing impression at the receiver position, a suitable model of the sound propagation will be implemented, which allows for a simulation in real time. In a last step, the partial sound source's signals will be convolved with the calculated sound propagation to synthesize the signal at the receiver position.

Marine soundscape and its temporal acoustic characterisation in the Gulf of Oristano, Sardinia (Western Mediterranean Sea)

The soundscape of the marine environment is a combination of geophony, biophony and anthropophony. Here, the soundscape of the Gulf of Oristano, a shallow inlet on the western coast of Sardinia including a special conservation area (Habitat Directive) and a national marine protected area, was investigated. Data collection was performed during July 2019, November 2019 and May 2020 using underwater acoustic equipment. The goal of this study was to characterise the ambient sound levels (Sound Pressure Level dB re 1 μPa) and describe the main soundscape components. The soundscape exhibited significant circadian and seasonal variations: the lowest and highest median SPL values were observed in the Spring (120–140 dB re 1 μPa; post-COVID-19 pandemic lockdown) and the Summer (128–150 dB re 1 μPa) respectively. Biophony was identified and characterised as dolphins’ ‘clicks’ and crustaceans’ ‘snapping’. Shrimp activity was dominant in the summer, while dolphin passages were observed across all sampling periods, accounting for 46.4% of the total recordings. Anthropophony, namely vessel passages, was predominant in the summer during the day-time and represented up to 42% of the acoustic space in the low-frequency band. Geophony increased low-frequency noise, and represented a highly variable component of the local soundscape. The marine soundscape is a valuabletool for defining integrated management plans for marine ecosystems, allowing the assessment of habitat quality, characterisation of sound sources and evaluation of the impact of anthropogenic activities.

Characterisation of acoustic louvres panel for Heating Ventilating and Air Conditioning (HVAC) noise control

This paper presents the results of research about louvre panels with 4 blades, 5 blades, and 6 blades for mechanical and acoustical performance which installed at the outlet of the ducting system. The mechanical performance will show up the airflow velocity and pressure drop, for the acoustical performance will analysed for its ability to reduce noise in the HVAC System. The measurement method used a rectangular linear duct with the inlet of a fan as an airflow source and loudspeaker as a noise source. The ability tested from the acoustic parameters of TL and the directivity of the noise from the outlet section, as well as mechanical analysis performance based on airflow and pressure drop. For the pressure drop parameter value is up to 20 Pa for 4 blades louvre, and about 24 Pa for 5 blades and 6 blades louvre. By using third octave band filter from 20 to 8000 Hz, the highest TL value is at 27 dB at a frequency of 63 Hz. For the directivity used to determine the distribution of sound energy around the outlet, it shows that the highest SPL value is at a frequency of 1 kHz with the difference from the perpendicular angle of the outlet after being given a louvre acoustic panel of 12 dB. So, the installation of louvre panels has small of pressure drop effect, but it can be effective for noise reduction.

Semi-occluded Nasal Tract Exercises (SONTEs): Nasal Tube in Water Exercises Using Nasal Consonants

This study analyzes the effects of the vocal exercises called semi-occluded nasal tract exercises (SONTEs), which were carried out with a new appliance that extends the nasal cavity as a part of the vocal tract. The acoustic, aerodynamic and electroglottographic (EGG) measurements were compared with those of the traditional semi-occluded vocal tract exercises (SOVTEs) of phonation in water. In this study, 34 women were randomly asked to perform phonation in water for 5 min through the nasal and oral routes with the sounds /m/ and /ɔ/, respectively, using a tube with a submersion depth of 5 cm. The acoustic, aerodynamic and EGG measurements before and after the exercises were analyzed using the appropriate statistical methods. No significant difference was found in the time and frequency domain parameters before and after the exercises, except for the amplitude perturbation quotient (APQ) values, which decreased after both exercises. In addition, there was no significant difference in any aerodynamic parameters before and after the exercises, but the mean SPL values significantly increased after both exercises. The oral and nasal peak inspiratory flow rates increased after both exercises, but the increase peaked after the SONTEs implementation. As expected, the EGG-jitter and EGG-periodicity values had a reciprocal interaction with each other, while differences were observed between the values of the vocal fold movements measured in both exercises. SONTEs may be as effective as the conventional SOVTEs because it made tube phonation into water possible through artificial extension of the nasal cavity and increased the resonant effect by using the positive effects based on the principles of SOVTEs.

The sound of recovery: Coral reef restoration success is detectable in the soundscape

Abstract Pantropical degradation of coral reefs is prompting considerable investment in their active restoration. However, current measures of restoration success are based largely on coral cover, which does not fully reflect ecosystem function or reef health. Soundscapes are an important aspect of reef health; loud and diverse soundscapes guide the recruitment of reef organisms, but this process is compromised when degradation denudes soundscapes. As such, acoustic recovery is a functionally important component of ecosystem recovery. Here, we use acoustic recordings taken at one of the world's largest coral reef restoration projects to test whether successful restoration of benthic and fish communities is accompanied by a restored soundscape. We analyse recordings taken simultaneously on healthy, degraded (extensive historic blast fishing) and restored reefs (restoration carried out for 1–3 years on previously degraded reefs). We compare soundscapes using manual counts of biotic sounds (phonic richness), and two commonly used computational analyses (acoustic complexity index [ACI] and sound‐pressure level [SPL]). Healthy and restored reef soundscapes exhibited a similar diversity of biotic sounds (phonic richness), which was significantly higher than degraded reef soundscapes. This pattern was replicated in some automated analyses but not others; the ACI exhibited the same qualitative result as phonic richness in a low‐frequency, but not a high‐frequency bandwidth, and there was no significant difference between SPL values in either frequency bandwidth. Furthermore, the low‐frequency ACI and phonic richness scores were only weakly correlated despite showing a qualitatively equivalent overall result, suggesting that these metrics are likely to be driven by different aspects of the reef soundscape. Synthesis and applications. These data show that coral restoration can lead to soundscape recovery, demonstrating the return of an important ecosystem function. They also suggest that passive acoustic monitoring (PAM) might provide functionally important measures of ecosystem‐level recovery—but only some PAM metrics reflect ecological status, and those that did are likely to be driven by different communities of soniferous animals. Recording soundscapes represents a potentially valuable tool for evaluating restoration success across ecosystems, but caution must be exercised when choosing metrics and interpreting results.

Assessment of Changes in Laryngeal Configuration and Voice Parameters Among Different Frequencies of Neuromuscular Electrical Stimulation (NMES) and Cumulative Effects of NMES in a Normophonic Subject: A Pilot Study

Neuromuscular electrical stimulation (NMES) is a complementary resource to voice therapy that can be used for the treatment of hypofunctional voice disorders. Although positive clinical studies have been reported, neutral and even potentially harmful effects of NMES are also described in the literature. Furthermore, in the studies examined by the authors, the use of different methods of NMES have been identified, which further contributes to the inconsistent results found among studies. Moreover, limited rationale is provided for the chosen NMES parameters such as electrode placement, frequency of NMES and length of treatment. The aims of this pilot study were to investigate the a) impact of different frequencies of NMES on glottal configuration and vocal fold vibration patterns and b) changes in laryngeal configuration and vocal output across 12 minutes of NMES. Three experiments were carried out looking at changes in laryngeal configuration and voice output using different imaging techniques (fibreoptic nasolaryngoscopy and high-speed video), acoustical analysis (F0, formant analysis, SPL, CPPS and LHSR values), electroglottography (EGG) and Relative Fundamental Frequency (RFF) analyses. Glottal parameters and acoustical measures were recorded before, during, and after stimulation. Data was collected at rest and during phonation. Overall the results showed global changes in laryngeal configuration from normal to hyperfunctional (ie, increased RFF, SPL, CQ, and stiffness). Changes were more pronounced for lower frequencies of NMES and were significant within less than three minutes of application. NMES is an effective resource for the activation of intrinsic laryngeal muscles producing significant levels of adduction within few minutes of application. Lower NMES frequencies produced greater muscle activation when compared to higher frequencies.

Dampak Kejadian La Niña Terhadap Curah Hujan Di Kabupaten Jembrana

Rainfall variability in Indonesia could be affected by global phenomenon like La NiA±a by looking at the intensity value of Southern Oscillation Index (SOI) and anomaly value of SPL. The amount of these effect varies from one place to another. Jembrana Regency is one of the Regency of Bali Province. Jembrana Regency is located at 8°09'30 - 8°28'02 SL and 114°25'53 - 114°56'38 EL. The west and south border of Jembrana Regency are the sea which are Bali Strait and Indian Ocean, whereas the its east and north border are Buleleng Regency and Tabanan Regency. Rainfall pattern of Jembrana Regency has a peak of the rainy season between December - February and a valley of the dry season between June - August. From monthly rainfall data taken from the rain post of Poh Santen, Rambutsiwi, Palasari and Negara, descriptive statistical method was used to calculate the average monthly rainfall during the period of 30 years during period of 1981-2010. La NiA±a of 2010 affected the amounts of rainfall that is greater than its average in Jembrana Regency Bali. La NiA±a of 2010 affected the amounts of rainfall that is greater than La NiA±a period of the previous years.

Corrigendum

Corrigendum

A Simple Method to Obtain Basic Acoustic Measures From Video Recordings as Subtitles.

Sound pressure level (SPL) and fundamental frequency (fo) are very basic and important measures in the acoustical assessment of voice quality, and their variation influences also the vocal fold vibration characteristics. Most sophisticated laryngeal videostroboscopic systems therefore also measure and display the SPL and fo values directly over the video frames by means of a rather expensive special hardware setup. An alternative simple software-based method is presented here to obtain these measures as video subtitles. The software extracts acoustic data from the video recording, calculates the SPL and fo parameters, and saves their values in a separate subtitle file. To ensure the correct SPL values, the microphone signal is calibrated beforehand with a sound level meter. The new approach was tested on videokymographic recordings obtained laryngoscopically. The results of SPL and fo values calculated from the videokymographic recording, subtitles creation, and their display are presented. This method is useful in integrating the acoustic measures with any kind of video recordings containing audio data when inbuilt hardware means are not available. However, calibration and other technical aspects related to data acquisition and synchronization described in this article should be properly taken care of during the recording.

Acoustical characteristics of device system for chasing away birds at Ngurah Rai International Airport Denpasar Bali

Ngurah Rai International Airport Denpasar Bali has two models of the device for chasing away birds these are Mobile Model and Fixed Model. Acoustical characteristics of the device for chasing away birds is determined by two parameters: SPL and Frequency Responses as well as sound propagation in the free field outdoor acoustics, thus to analyze sound properties radiated by the device for chasing away birds must be using a theoretical approach of Inverse Distance Law. Measurement results on Mobile Model that decreasing value of SPL by moving microphone position into the position of double distances from an original distance were somewhat 6 dB, it is nearly agreed with Inverse Distance Law. While measurement results on Fixed Model using the same mechanism of changing the distance the decreasing value of SPL does not comply Inverse Distance Law since the decreasing is about 10 dB. From results of measurement of decreasing SPL, both two models of the device for chasing away birds can be only used effectively to disperse some birds in which their position is very near the speaker that is about 4 - 8 m. Based on a calculation using Inverse Distance Law, the value of SPL at the distance of 1 m from the speaker is below 100 dB. Measurement results on Frequency Spectrum for Mobile Model was dominant at the frequency of 500 Hz to 3150 Hz, while for Fixed Model was dominant at the frequency of 500 Hz to 2500 Hz. At the end, the device for chasing away birds using acoustical method needs a system of sound generator and speaker which can generate the sound wave with very high of sound power level and it has a flat form of frequency responses with a wide range of frequencies. With the high sound power level, the sound will reach very far away this kind of device is called Long Range Acoustic Device (LRAD).

An acoustic study of sea ice behavior in a shallow, Arctic bay

Recent acceleration of sea ice decline observed in the Arctic Ocean draws attention to environmental factors driving this phenomenon. One of the main conclusions is a growing need for better understanding of sea ice drift, deformation, and fracturing. In response to that call, several ambient noise recordings were carried out in the coastal zone of Hornsund Fjord, Spitsbergen, in spring 2015 to study underwater acoustic signatures of sea ice behavior. The noise levels varied significantly with sea ice type and intensity of external forces. Low-frequency signatures were strongly related to tidal cycle, which manifested in much higher SPL values at low water. Compacted ice cover is periodically deformed and crushed, representing a significant contribution to the ambient noise field in the study site. Average noise levels at frequencies above 1 kHz are, in turn, considerably higher in front of marine-terminating glacier than in the neighboring, non-glacial bay. These differences, expanding with the rise of water temperature, are associated with melting of the ice cliff and generally unaffected by the presence of sea ice. [Work funded by the Polish National Science Centre, Grant No. 2013/11/N/ST10/01729.]

Short Communication: The clay nanoparticle impregnation for increasing the strength and quality of sengon (Paraserianthes falcataria) and white meranti (Shorea bracteolata) timber

Alex T, Winarni B, Kusuma IW, Arung ET, Budiarso E. 2017. Short Communication: The clay nanoparticle impregnation for increasing the strength and quality of sengon (Paraserianthes falcataria) and white meranti (Shorea bracteolata) timber. Nusantara Bioscience 9: 107-110. The clay nanoparticle impregnation for increasing the strength and quality of sengon (Paraserianthes falcataria) and white meranti (Shorea bracteolata) timber. The clay nanoparticles as a fine particle material dissolved in water was impregnated into the sengon and white meranti timber in order to improve its strength properties. Impregnation is the process of inserting the material dissolved in specific water or liquid in the timber using vacuum tube and air pressure. Materials used in this study were clay nanoparticles and the sample test of sengon (P. falcataria) and white meranti (S.bracteolata) timbers with a size of 2 cm x 2 cm x 40 cm. A total of 30 samples for each type of dried timber were impregnated using clay nanoparticles with a pressure of 60 psi for 2 hours. The results showed that impregnation with clay nanoparticles at concentrations of 5% gave the retention value of sengon and white meranti timber of 22.73 kg.m3 and 24.89 kg.m3, respectively. Wood strength is indicated by the voltage value at the boundary proportion (SPL), modulus of rupture (MOR) and modulus of elasticity (MOE). sengon timber shows the value of SPL, MOR, MOE by 296.57 kg.cm2, 376.36 kg.cm2, and 38027.663 kg.cm2, while the white meranti timber had the value of SPL, MOR, MOE as follows: 623, 32 kg.cm2, 729.69 kg.cm2 and 160.187 kg.cm2. The strength of sengon timber was increased from class V (very low) to class IV (low), whereas white meranti was increased from class IV (low) into class II (strong).

Study on the Effect of Partition Heights in Open Plan Office to the Privacy and Distraction Level Utilizing Computational Fluid Dynamics

Open-plan office is a room designed without the use of full-height partitions to isolate a workstation from other workstations. Speech privacy is one of the acoustical problems related with communication activities of the workers. Previous studies have shown that there are several sound phenomena that were unable to be explored using computer simulation based on ray tracing method. This paper is attempted to find the influence of partition height of various designs to the privacy level based on computational fluid dynamic, especially using the acoustics diffusion equation method. The results show that variation of height partitions can lower sound pressure level value by 5% - 6%, variation of absorption coefficient can lower SPL value by 8% - 9%, and adding furniture as book shelves does not change the open-plan office privacy level significantly.

De-Frag: an efficient scheme to improve deduplication performance via reducing data placement de-linearization

Data deduplication has become a commodity in large-scale storage systems, especially in data backup and archival systems. However, due to the removal of redundant data, data deduplication de-linearizes data placement and forces the data chunks of the same data object to be divided into multiple separate units. In our preliminary study, we found that the de-linearization of data placement compromises the data spatial locality that is used to improve data read performance, deduplication throughput and deduplication efficiency in some deduplication approaches, which significantly affects deduplication performance and makes some deduplication approaches become less effective. In this paper, we first analyze the negative effect of data placement de-linearization to deduplication performance, and then propose an effective approach called De-Frag to reduce the de-linearization of data placement. The key idea of De-Frag is to choose some redundant data to be written to the disks rather than be removed. It quantifies the spatial locality of each chunk group by spatial locality level (SPL for short) and writes the redundant chunks to disks when SPL value is smaller than a preset value, thus to reduce the de-linearization of data placement and enhance the spatial locality. As shown in our experimental results driven by real world datasets, De-Frag effectively enhances data spatial locality and improves deduplication throughput, deduplication efficiency, and data read performance, at the cost of slightly lower compression ratios.

나노웹을 이용한 라미네이트소재의 마찰음 특성

This study examines the rustling sound characteristics of electrospun nanofiber web laminates according to layer structures. This study assesses mechanical properties and frictional sounds (such as SPL); in addition, Zwicker's psychoacoustic parameters (such as Loudness (Z), Sharpness (Z), Roughness (Z), and Fluctuation strength (Z)) were calculated using the Sound Quality Program (ver.3.2, B&K, Denmark). The result determined how to control these characteristics and minimize rustling sounds. A total of 3 specimens' frictional sound (generated at 0.63 m/s) was recorded using a Simulator for Frictional Sound of Fabrics (Korea Patent No. 10-2008-0105524) and SPLs were analyzed with a Fast Fourier Transformation (FFT). The mechanical properties of fabrics were measured with a KES-FB system. The SPL value of the sound spectrum showed 6.84~58.47dB at 0~17,500Hz. The SPL value was 61.2dB for the 2-layer PU nanofiber web laminates layered on densely woven PET(C1) and was the highest at 65.1dB for the 3-layer PU nanofiber web laminates (C3). Based on SPSS 18.0, it was shown that there is a correlation between mechanical properties and psychoacoustic characteristics. Tensile properties (LT), weight (T), and bending properties (2HB) showed a high correlation with psychoacoustic characteristics. Tensile linearity (LT) with Loudness (Z) showed a negative correlation coefficient; however, weight (T) with Sharpness (Z) and Roughness (Z), and bending hysteresis (2HB) with Roughness (Z) indicated positive correlation coefficients, respectively.

PTFE(Polytetrafluoroethylene) 라미네이팅 투습발수직물의 총음압 최소화를 위한 필름 타입 별 기본 특성과 역학 특성

This study investigates the sound properties of fabric frictional sound (SPL, <TEX>${\Delta}L$</TEX>, <TEX>${\Delta}f$</TEX>) according to the film type of PTFE laminated vapor-permeable water-repellent fabrics in order to understand the relationship between SPL and the basic properties of fabrics such as layer, yarn type, and thickness of fiber. This study accesses their mechanical properties and determines how to control them to minimize SPL. Eight PTFE laminated water-repellent fabrics, composed of four different film types (A, B, C, D) and with two different fabrics, were used as test specimens. Frictional sounds generated at 1.21m/s were recorded by using a fabric sound generator and SPLs were analyzed through Fast Fourier Transformation (FFT). The mechanical properties of fabrics were measured by KES-FB. The SPL value was lowest at 74.4dB in film type A and highest as 85.5dB in type D. Based on ANOVA and post-hoc test, specimens were classified into less Loud Group (A, B) and Loud Group (C, D). It was shown that SPL was lower when 2 layer (instead of 3 layer), filament yarn than staple, and thin fiber than thick were used. In Group I, shearing properties (G, 2HG5), geometrical roughness (SMD), compressional properties (LC, RC) and weight (W) showed high correlation with SPL however, elongation (EM) and shear stiffness (G) did with SPL in Group II.

Chapter 7: Effects of gas-well-compressor noise on the ability to detect birds during surveys in northwest New Mexico

we used three site types to address whether noise from gas well compressors interfered with our ability to detect birds in the Rattlesnake Canyon Habitat management Area, San Juan County, New mexico: (1) gas wells without compressors (control), (2) gas wells with compressors turned off only during surveys (T-off), and (3) gas wells with compressors running during the surveys (T-on). we conducted 571 bird surveys at 294 point-count loca- tions, which were 50-150 m from gas well pads. we measured sound pressure levels (SPls) at point locations: control mean = 38.6 ± 3.0 (Sd) db(A); T-off mean = 55.0 ± 5.2 db(A), measured with compressors on; and T-on mean = 52.7 ± 4.5 db(A). w e observed significant differences in species richness, individual abundance, and bird diversity among site types; the differences existed between control and T-on sites and between T-off and T-on sites, but not between control and T-off sites. Species richness, individual abundance, and species diversity were all signifi- cantly and negatively influenced by SPl values. A significantly higher proportion of birds were detected on T-off sites compared with T-on sites for 13 species; this compares with only one species that was detected more at T-on sites than at T-off sites. Our results strongly suggest that noise emitted from gas well compressors significantly impaired our ability to detect birds. w e determined that the detection threshold is ~45 db(A), beyond which noise impairs human abil- ity to detect birds within 60 m. These results are relevant to bird surveys in areas where natural and anthropogenic noise may negatively bias detections.