Low Sound Levels Research Articles

Acoustic Characterization around the CalWave Wave Energy Converter

Sound generated by marine energy (ME) installations in the ocean environment remains a particular concern for environmental permitting despite the limited evidence showing low levels of ME sounds relative to other anthropogenic sounds. In an effort to increase understanding of potential environmental effects of marine energy projects and help reduce barriers to marine energy deployments, a new acoustic monitoring technology, the NoiseSpotter®, was developed and recently demonstrated around CalWave’s operational scaled xWave™ wave energy converter (WEC). The NoiseSpotter® improves upon traditional acoustic sensing techniques by use of a cost-effective, compact array of acoustic particle velocity sensors that characterizes, classifies, and provides accurate location information for anthropogenic and natural sounds in real time. Results are presented from co-deployments of NoiseSpotter® with the operational CalWave WEC that were conducted over a 9-day period in fall 2021 offshore of Scripps Research Pier in San Diego, California, USA. The multi-day deployment of the NoiseSpotter® at 100 m from the CalWave WEC revealed a rich library of sounds that include: Low-level (~95 dB re 1 µPa relative to an ambient noise floor between 80-90 dB re 1 µPa) sounds from the WEC associated with the deliberate actuation of mechanical components, Sounds from a hovering helicopter, Marine mammal vocalizations, and, Small boat engines. Sound levels from the WEC were placed within the context of ambient sounds, and reveal little deviation from the ambient soundscape. The azimuthal anisotropy of WEC sound was investigated via deployments along four cardinal directions around the WEC. While a noticeable increase was observed along the north-south orientation, the sound levels along all directions still showed little deviation relative to the ambient noise floor. Analysis of low-level WEC sounds in conjunction with exploratory machine learning techniques demonstrate the utility of directional acoustic sensing in distinguishing marine energy sounds from the myriad other sounds in the surrounding ocean environment.

A pilot study on spatial hearing in children with congenital unilateral aural atresia.

Despite normal hearing in one ear, individuals with congenital unilateral aural atresia may perceive difficulties in everyday listening conditions typically containing multiple sound sources. While previous work shows that intervention with bone conduction devices may aid spatial hearing for some children, testing conditions are often arranged to maximize any benefit and are not very similar to daily life. The benefit from amplification on spatial tasks has been found to vary between individuals, for reasons not entirely clear. This study has sought to expand on the limited knowledge on how children with unilateral aural atresia recognize speech masked by competing speech, and how horizontal sound localization accuracy is affected by the degree of unilateral hearing loss and by amplification using unilateral bone conduction devices when fitted before 3 years of age. In a within-subject, repeated measures design, including 11 children (mean age = 7.9 years), bone conduction hearing device (BCD) amplification did not negatively affect horizontal sound localization accuracy. The effect on speech recognition scores showed greater inter-individual variability. No benefit from amplification on a group level was found. There was no association between age at fitting and the benefit of the BCD. For children with poor unaided sound localization accuracy, there was a greater BCD benefit. Unaided localization accuracy increased as a function of decreasing hearing thresholds in the atretic ear. While it is possible that low sound levels in the atretic ear provided access to interaural localization cues for the children with the lowest hearing thresholds, the association has to be further investigated in a larger sample of children.

Development of a test rig for the investigation of flow-induced mechanisms of sound generation at radial fans

A low sound pressure level is a crucial quality feature for industrial and non-industrial radial fans. The scientific literature documents numerous mechanisms of flow-induced sound generation that can occur in a radial fan. Nevertheless, not all sound generation mechanisms are considered well-understood today and thus are still dealt with in ongoing research. This work develops an experimental setup to investigate the different mechanisms of flow-induced sound generation in radial fans. The aim is to close the existing gap between available experimental research on axial and radial fans. One critical factor for the experimental investigation of flow-induced sound generation in fans is the control of inflow. Due to the design of radial fans, the fluid flow deflects from the axial supply duct to the radial direction upstream of the impeller, generating a complex flow field with limited control possibilities. Hence, we designed a test rig that improves the control of inflow conditions, aiming to resolve the superposed sound generation mechanisms in acoustic measurements. This paper presents the key features of the test rig and some first experimental results. The investigation of the distinct sound generation mechanisms is left to future work based on the introduced test rig.

Interaural frequency mismatch jointly modulates neural brainstem binaural interaction and behavioral interaural time difference sensitivity in humans

The binaural interaction component (BIC) of the auditory brainstem response (ABR) is the difference obtained after subtracting the sum of right and left ear ABRs from binaurally evoked ABRs. The BIC has attracted interest as a biomarker of binaural processing abilities. Best binaural processing is presumed to require spectrally-matched inputs at the two ears, but peripheral pathology and/or impacts of hearing devices can lead to mismatched inputs. Such mismatching can degrade behavioral sensitivity to interaural time difference (ITD) cues, but might be detected using the BIC. Here, we examine the effect of interaural frequency mismatch (IFM) on BIC and behavioral ITD sensitivity in audiometrically normal adult human subjects (both sexes). Binaural and monaural ABRs were recorded and BICs computed from subjects in response to narrowband tones. Left ear stimuli were fixed at 4000 Hz while right ear stimuli varied over a ∼2-octave range (re: 4000 Hz). Separately, subjects performed psychophysical lateralization tasks using the same stimuli to determine ITD discrimination thresholds jointly as a function of IFM and sound level. Results demonstrated significant effects of IFM on BIC amplitudes, with lower amplitudes in mismatched conditions than frequency-matched. Behavioral ITD discrimination thresholds were elevated at mismatched frequencies and lower sound levels, but also more sharply modulated by IFM at lower sound levels. Combinations of ITD, IFM and overall sound level that resulted in fused and lateralized percepts were bound by the empirically-measured BIC, and also by model predictions simulated using an established computational model of the brainstem circuit thought to generate the BIC.

Momentum Iterative Fast Gradient Sign Algorithm for Adversarial Attacks and Defenses

Deep neural networks (DNNs) are particularly vulnerable to adversarial samples when used as machine learning (ML) models. These kinds of samples are typically created by combining real-world samples with low-level sounds so they can mimic and deceive the target models. Since adversarial samples may switch between many models, black-box type attacks can be used in a variety of real-world scenarios. The main goal of this project is to produce an adversarial assault (white box) using PyTorch and then offer a defense strategy as a countermeasure. We developed a powerful offensive strategy known as the MI-FGSM (Momentum Iterative Fast Gradient Sign Method). It can perform better than the I-FGSM because to its adaptation (Iterative Fast Gradient Sign Method). The usage of MI-FGSM will greatly enhance transferability. The other objective of this project is to combine machine learning algorithms with quantum annealing solvers for the execution of adversarial attack and defense. Here, we'll take model-based actions based on the existence of attacks. Finally, we provide the experimental findings to show the validity of the developed attacking method by assessing the strengths of various models as well as the defensive strategies.

EEG alpha wave responses to sounds from neighbours in high-rise wood residential buildings

This study explored electroencephalogram (EEG) alpha waves (α-EEG) in response to neighbours’ sounds in wood residential buildings. Experiments were carried out in a laboratory to collect α-EEG data in distinct acoustics scenarios. A series of impact and airborne sounds were generated using loudspeakers and subwoofers, while the participants sat comfortably in a simulated living room wearing EEG headsets. Impact sounds were those of footsteps of adults walking on floors equipped with different timber floor configurations, whereas airborne sounds were of speech and music digitally filtered to resemble the good and poor sound insulation performances of lightweight vertical partitions. The sound sources were presented both individually and in combination (e.g. footsteps combined with music or speech). Noise sensitivity and attitudes towards neighbours were introduced as non-acoustic factors. The study highlighted significantly higher α-EEG in response to footsteps heard through floors characterised by low impact sound pressure levels (SPL) and to music heard through partition walls with low sound reduction indices. The effective duration of the autocorrelation function, τe, was computed to investigate subjective preference, and significant differences between sounds heard at various SPLs were identified for speech and music. Footsteps sounds in combination with an airborne source elicited higher α-EEG when compared to single footsteps sounds. Participants with self-reported low noise-sensitivity and positive attitude towards neighbours showed significantly larger α-EEG responses when exposed to sounds from neighbours than those who had high noise-sensitivity and negative attitude towards neighbours.

Measurement of swept level distortion product otoacoustic emission growth functions at multiple frequencies simultaneously.

Otoacoustic emissions (OAEs) are low-level sounds generated by the inner ear that provide a non-invasive assessment of cochlear health. Advanced applications require recording OAEs across a wide range of frequencies and stimulus levels. Detailed here is a method for efficiently measuring distortion product otoacoustic emissions (DPOAEs) across an expansive stimulus space. Specifically, DPOAEs are recorded by sweeping the evoking stimuli in level across multiple frequencies simultaneously. This method generates DPOAE growth functions at multiple f2 frequencies in several minutes. Results indicate the swept level method yields DPOAEs equivalent to those measured in a traditional (discrete stimulus) paradigm, but with several advantages.

Temporal variability of a soundscape near a mid-oceanic atoll in the northern Indian ocean

Soundscape ecology in the context of physical oceanographic features is an emerging area of research revealing interactions between physically, biologically and anthropogenically driven sounds and their sources. Soundscapes can shape and reveal distributions of a range of species, from fish larvae to whales, within marine ecosystems. The northern Indian Ocean is a region of high environmental variability driven by seasonally reversing monsoonal winds. The mid-oceanic islands within these waters consist of steep slopes forming a crucial interface between shallow reef and deep oceanic habitats. Studies on soundscape are limited in these waters. The aim of this study was to characterize major sound sources off the southern and northern side of the Kavaratti atoll in Lakshadweep islands, India, located at the northern part of the Laccadive-Maldives-Chagos Ridge. A first look at shallow water soundscapes are provided here using passive acoustic monitoring, and how they correlate with satellite-derived oceanographic variables. Geophonic and biophonic sources across different frequency bands are identified with three major choruses – a dusk fish chorus, a midnight chorus that is speculated to be produced by myctophids, and a snapping shrimp night chorus. Low frequency biophonic choruses peaked in inter-monsoon months (January to March), while low frequency geophonic sound levels peaked during monsoon months (June to October) and increased with wind speed. The dusk fish chorus and the midnight chorus (at the south site) decreased with increasing sea surface salinity, while the snapping shrimp chorus (at the south site) increased with increasing sea surface salinity. Snapping shrimp chorus levels increased with decreasing wind speed. The dusk fish chorus peaked during full and waning moon, and the midnight and snapping shrimp choruses peaked during new moon periods. The sources and patterns described in this study will help compare with future soundscape and sound pressure level measurements within this region. This will be useful in the context of a changing climate and for planning future developmental projects on the islands. Reef choruses link with peak larval recruitment, spawning, or feeding activities, and further investigation into the peak calling times reported here will help uncover the function of choruses. Expanding the collection of passive acoustic monitoring data and oceanographic measurements over longer timescales will significantly advance ‘soundscape oceanography’.

The effect of water sound level in virtual reality: A study of restorative benefits in young adults through immersive natural environments

Virtual Reality (VR) can bring a person to a restorative natural environment—an immersive experience containing elements from blue and green space that help reduce stress and anxiety. However, the effect of different water sound levels on psychological and physiological health remains unclear. This study used a VR natural environment—combining forest scene and waterfall sounds—to compare the low and high water sound levels' effects on individuals' psychological (affective quality of place and state anxiety relief) and physiological benefits (heart rate variability). We focused on two comparisons in each of the two dimensions: (1) a before-and-after comparison that analyzes the effectiveness of the water sounds, and (2) a low-and-high comparison that investigates the differences between the two sound levels. A total of 45 university students (aged between 19 and 23) participated in the experiment. The results show that both low- and high-decibel levels improved in psychological dimension, and decrease individuals’ heart rates from anxiety status. More importantly, while the high-decibel served to awaken emotions, the low-decibel was more effective at calming emotions and relieving anxiety. Overall, we found that natural waterscape sounds relieve transient anxiety states and promote healthy autonomic nervous activity. This study provides evidence for the planning of healthy environmental interaction patterns and the design of urban soundscapes.

335 Sources of Sound Exposure in Pediatric Critical Care

OBJECTIVES/GOALS: Sleep is critical for healing, however pediatric intensive care unit (PICU) sound is above recommended levels (i.e., 45 A-weighted decibels [dBA]). This observational study identifies sources of PICU sound and compares sources between times of high (i.e., dBA≥45) and low (i.e., dBA < 45) levels. METHODS/STUDY POPULATION: The sound environment of 10 critically ill children 1 to 4 years of age was monitored via a bedside dosimeter and video camera for 48 hours, or until PICU discharge. Dosimeter and video data were uploaded to Noldus Observer XT and time synchronized. A reliable, previously published coding scheme developed to identify sound sources in the adult ICU was modified for the pediatric population. Sound sources (e.g., clinician/family/child [verbal vs. non-verbal] vocalization, patient care, medical equipment) were identified via instantaneous sampling of video data at each minute of recording. The proportion of sampling points with each sound source are compared between times of high and low sound levels, and between day (7:00-18:59) and night (19:00-6:59) shift. RESULTS/ANTICIPATED RESULTS: Video coding is ongoing, with high inter-rater reliability (κ̅=0.99, SD DISCUSSION/SIGNIFICANCE: Medical equipment sound is ubiquitous in the PICU. Clinicians should optimize the PICU sound environment for sleep, including minimizing equipment alarms, conversation, general activity, and screen media during child rest. Large-scale studies are needed to confirm findings from this small cohort.

Relationships between loudness and preference judgments for fan sounds as a function of the reference sound pressure level

In a prior study, the level of fan test sounds was adjusted in a listening test using an adaptive procedure, until they became equally loud or equally preferred as a reference sound at a fixed level. Depending on the test sound, level reductions of up to 15 dB compared to the 60 dB(A) reference level were necessary to reach equal loudness or preference compared to the reference sound. It turned out that the preference-equivalent levels were highly correlated with the loudness-equivalent levels, indicating that the preference decision and the loudness judgment were closely related to each other. In a follow-up study, the measurements were extended towards a higher reference level of 75 dB(A) and a lower reference level of 45 dB(A). The preference-equivalent levels obtained at 75 dB(A) were again closely related to the loudness-equivalent levels. For the lower reference level of 45 dB(A), the preference-equivalent levels deviate from the loudness-equivalent levels by 3.5 dB on average and also the inter-individual variability increased. This result suggests an increasing effect of additional fan-noise characteristics to play a role for the preference decisions on top of the perceived loudness especially at low absolute sound pressure levels.

Assessing the influence of street canyon shape on aircraft noise: results from measurements in courtyards near Amsterdam Schiphol Airport.

Aircraft noise prediction models traditionally omit buildings to optimize speed. Buildings and vertical surfaces scatter and reflect incident sound, affecting sound levels around buildings and within streets. Previous studies showed the impact of buildings on aircraft noise, based on a small number of measurements. Based on additional numerical models, it was found that the shape of buildings, i.e. a slanted or overhanging roof, lead to lower sound levels compared to streets comprised of vertical and flat surfaces. To examine these findings, a full-scale field lab was built near Amsterdam Schiphol Airport, comprised of shipping containers. The experiment consists of three courtyards, in which ten microphones measure sound levels from aircraft flyovers, near facades facing towards and away from the sound source (airplanes). Measurements are matched with meteorological and radar data, which gives information about the position of aircraft and the local weather conditions. The measurements show substantial differences depending on the position, ranging between 11dB(A) for a courtyard with straight facades, up to 14dB(A) for facades in a courtyard with a slanted roof and a roof overhang. Results can be used to rethink the way areas near airports are designed.

Metabolic and Sensory Components of Age-Related Hearing Loss: Associations With Distortion- and Reflection-Based Otoacoustic Emissions.

Age-related hearing loss is difficult to study in humans because multiple genetic and environmental risk factors may contribute to pathology and cochlear function declines in older adults. These pathologies, including degeneration of the stria vascularis, are hypothesized to affect outer hair cells responsible for active cochlear amplification of low-level sounds. Otoacoustic emission (OAE) measures are used to quantify the energy added to the traveling wave in cochlear amplification, which typically weakens with increased pure-tone thresholds and for older individuals. Thus, the current study evaluated two OAE measures for individuals with different components of age-related hearing loss. We examined two retrospective adult lifespan datasets (18 to 89+ years of age) from independent sites (Medical University of South Carolina and Boys Town National Research Hospital), which included demographics, noise history questionnaires, distortion-product otoacoustic emissions (DPOAE), and cochlear reflectance (CR). Metabolic and sensory estimates of age-related hearing loss were derived from the audiograms in each dataset, and then tested for associations with DPOAE and CR. The results showed that metabolic estimates increased for older participants and were associated with lower overall DPOAE and CR magnitudes across frequency (i.e., lower fitted intercepts). Sensory estimates were significantly higher for males, who reported more positive noise histories compared to females and were associated with steeper negative across-frequency slopes for DPOAEs. Although significant associations were observed between OAE configurations, DPOAEs appeared uniquely sensitive to metabolic estimates. The current findings suggest that distortion-based measures may provide greater sensitivity than reflection-based measures to the components of age-related hearing loss.

Usefulness of phase gradients of otoacoustic emissions in auditory health screening: An exploration with swept tones.

Otoacoustic emissions (OAEs) are low-level sounds generated by the cochlea and widely used as a noninvasive tool to inspect cochlear impairments. However, only the amplitude information of OAE signals is used in current clinical tests, while the OAE phase containing important information about cochlear functions is commonly discarded, due to the insufficient frequency-resolution of existing OAE tests. In this study, swept tones with time-varying frequencies were used to measure stimulus frequency OAEs (SFOAEs) in human subjects, so that high-resolution phase spectra that are not available in existing OAE tests could be obtained and analyzed. The results showed that the phase of swept-tone SFOAEs demonstrated steep gradients as the frequency increased in human subjects with normal hearing. The steep phase gradients were sensitive to auditory functional abnormality caused by cochlear damage and stimulus artifacts introduced by system distortions. At low stimulus levels, the group delays derived from the phase gradients decreased from around 8.5 to 3 ms as the frequency increased from 1 to 10 kHz for subjects with normal hearing, and the pattern of group-delay versus frequency function showed significant difference for subjects with hearing loss. By using the swept-tone technology, the study suggests that the OAE phase gradients could provide highly sensitive information about the cochlear functions and therefore should be integrated into the conventional methods to improve the reliability of auditory health screening.

Estimating human neural tuning curves at low-level sound from human psychophysical masking data and the cochlea-frequency maps

We proposed a three-slope method to estimate human frequency tuning curves at low sound levels. As a starting point, cat neural excitation patterns (Allen and Fahey, 1993) are derived from Liberman’s cat cochlea neural tuning curves data (Liberman, 1978) in a mathematical way. A three-slope structure inspired by (Rhode,1978) is proposed to represent neural excitation patterns. The aim of this paper is to estimate the three-slope structure for human neural excitation patterns and then transform human neural excitation patterns into human tuning curves by using a human cochlea-frequency map (Greenwood, 1990). In 1993, Allen and Fahey introduced the concept of the second cochlea map, which was shown to be highly correlated with both neural excitation patterns and distortion product otoacoustic emissions (DPOAE). Thus, three slopes of human neural excitation patterns may be estimated via the second cochlea map and human masking data (Wegel and Lane, 1924). In the present study, slopes are estimated from limited existing psychophysical data, which can be improved with more accurate experimental data in the future.

Image quality and subject experience of quiet T1-weighted 7-T brain imaging using a silent gradient coil

ObjectivesAcoustic noise in magnetic resonance imaging (MRI) negatively impacts patients. We assessed a silent gradient coil switched at 20 kHz combined with a T1-weighted magnetisation prepared rapid gradient-echo (MPRAGE) sequence at 7 T.MethodsFive healthy subjects (21–29 years; three females) without previous 7-T MRI experience underwent both a quiet MPRAGE (Q-MPRAGE) and conventional MPRAGE (C-MPRAGE) sequence twice. Image quality was assessed quantitatively, and qualitatively by two neuroradiologists. Sound level was measured objectively and rated subjectively on a 0 to 10 scale by all subjects immediately following each sequence and after the whole examination (delayed). All subjects also reported comfort level, overall experience and willingness to undergo the sequence again.ResultsCompared to C-MPRAGE, Q-MPRAGE showed higher signal-to-noise ratio (10%; p = 0.012) and lower contrast-to-noise ratio (20%; p < 0.001) as well as acceptable to good image quality. Q-MPRAGE produced 27 dB lower sound level (76 versus 103 dB). Subjects reported lower sound level for Q-MPRAGE both immediate (4.4 ± 1.4 versus 6.4 ± 1.3; p = 0.007) and delayed (4.6 ± 1.4 versus 6.3 ± 1.3; p = 0.005), while they rated comfort level (7.4 ± 1.0 versus 6.1 ± 1.7; p = 0.016) and overall experience (7.6 ± 1.0 versus 6.0 ± 0.9; p = 0.005) higher. Willingness to undergo the sequence again was also higher, however not significantly (8.1 ± 1.0 versus 7.2 ± 1.3; p = 0.066).ConclusionQ-MPRAGE using a silent gradient coil reduced sound level by 27 dB compared to C-MPRAGE at 7 T while featuring acceptable-to-good image quality and a quieter and more pleasant subject experience.

Effects of Industrial Noise on Physiological Responses

Noise pollution is one of the most common workplace hazards. Noise exposure may induce auditory and extra-auditory physiological and psychological alterations that affect job performance, safety, comfort, and wellbeing. Recent research showed a connection between frequency components of noise and health outcomes, annoyance, physiological and psychological changes. This study investigated whether and how the activation of different typologies of industrial noises set at three different sound levels induced increases in electrodermal activity (EDA) and the heart rate variations differently. A laboratory listening test was performed for the study, in which 24 subjects were exposed to the activation of different industrial noises: Low Frequency, High Frequency, and Modulated noises at Low, Medium, and High sound levels, while some physiological responses were recorded. The noise stimuli were also evaluated based on a self-report questionnaire. Results show that the EDA variation increases as the Sound Level increases and is higher at HF. In contrast, no relevant changes have been found in RR variation. EDA changes are also related to the perception of the Valence dimension of the noise environment, while RR variations not. The findings of this study emphasized that the changes in EDA depend on the sound levels and frequency content of industrial noise typologies, as well as on the perception of their Valence.

Research on detection and recognition methods of gas pipelines based on acoustic signal feature analysis

In the process of reconstruction and expansion of gas pipeline, it is easy to destroy in-service gas pipeline and cause safety accidents. In order to realize the detection of in-service pipelines, based on the characteristics of low sound pressure level and easy attenuation of acoustic signals of gas pipelines, the detection and identification method of gas pipelines based on acoustic signal feature analysis was studied by using Hilebert–Huang transform algorithm and optimized Back Propagation (BP) neural network. This method takes the gas pipeline flow noise signals obtained by numerical simulation and experimental verification as the research object, and the underwater acoustic signals are collected for comparative analysis. Empirical Mode Decomposition (EMD) was used to decompose the two signals, and the time-domain waveform of Intrinsic Mode Functions (IMF) component was obtained, and the characteristic parameters of peak value and peak frequency were determined. The energy characteristic parameters of Hilbert marginal spectrum were calculated, and the characteristic database of gas pipeline flow noise signal was obtained. The optimized BP neural network was used for pattern recognition. The results show that the identification rate of gas pipeline acoustic signal can reach 97.5% by using this method, which verifies the effectiveness of the gas pipeline detection and identification method in this paper.

Noise Levels and Sleep in a Surgical ICU

Sleep is disturbed in critically ill patients and is a frequently overlooked complication. The aim of our study is to evaluate the impact of sound levels in our surgical ICU on our patients’ sleep on the first night of admission. The study was performed in a tertiary care university hospital, in a 12-bed surgical ICU. Over a 6-week period, a total of 148 adult, non-intubated and non-sedated patients completed the study. During this six-week period, sound levels were continuously measured using a type II sound level meter. Sleep quality was evaluated using the Richards–Campbell Sleep Questionnaire (RCSQ), which was completed both by patients and nurses on the first morning after admission. A non-significant correlation was found between night sound levels and sleep quality in the overall sample (r = −1.83, 95% CI; −4.54 to 0.88, p = 0.19). After multivariable analysis, a correlation was found between higher sound levels at night and lower RCSQ evaluations (r = −3.92, 95% CI; −7.57 to −0.27, p = 0.04). We found a significant correlation between lower sound levels at night and a better quality of sleep in our patients; for each 1 dBA increase in LAFeq sound levels at night, patients scored 3.92 points lower on the sleep questionnaire.

A silent two-photon imaging system for studying in vivo auditory neuronal functions

Two-photon laser-scanning microscopy has become an essential tool for imaging neuronal functions in vivo and has been applied to different parts of the neural system, including the auditory system. However, many components of a two-photon microscope, such as galvanometer-based laser scanners, generate mechanical vibrations and thus acoustic artifacts, making it difficult to interpret auditory responses from recorded neurons. Here, we report the development of a silent two-photon imaging system and its applications in the common marmoset (Callithrix Jacchus), a non-human primate species sharing a similar hearing range with humans. By utilizing an orthogonal pair of acousto-optical deflectors (AODs), full-frame raster scanning at video rate was achieved without introducing mechanical vibrations. Imaging depth can be optically controlled by adjusting the chirping speed on the AODs without any mechanical motion along the Z-axis. Furthermore, all other sound-generating components of the system were acoustically isolated, leaving the noise floor of the working system below the marmoset’s hearing threshold. Imaging with the system in awake marmosets revealed many auditory cortex neurons that exhibited maximal responses at low sound levels, which were not possible to study using traditional two-photon imaging systems. This is the first demonstration of a silent two-photon imaging system that is capable of imaging auditory neuronal functions in vivo without acoustic artifacts. This capacity opens new opportunities for a better understanding of auditory functions in the brain and helps isolate animal behavior from microscope-generated acoustic interference.