Major Noise Sources Research Articles

Small Vessel Impact on the Whistle Parameters of Two Ecotypes of Common Bottlenose Dolphin (Tursiops truncatus) in La Paz Bay, Mexico

Vessel traffic is one of the major sources of underwater anthropogenic noise. Dolphins can modify their vocal repertoire, especially whistles, in presence of vessels to facilitate their communication. Acoustic data were collected (sampling rate 96 kHz) in La Paz Bay, Gulf of California, Mexico. Whistle rate and parameters of the coastal and oceanic ecotypes of common bottlenose dolphins (Tursiops truncatus) were measured in absence of vessels and in presence of moving small vessels (size 5–10 m). The peak noise difference was calculated between the two frequency bands dominated by the whistles (2000–20,000 Hz) and the small vessel (500–2000 Hz). In presence of vessels the oceanic ecotype decreased whistle frequencies while the coastal ecotype increased them. Both ecotypes raised whistle frequencies with the decreasing of the peak noise difference. The differences in habitat and group structure could have driven the two ecotypes to react in a different way to the vessel presence.

Postprocessing subtraction of tilt-to-length noise in LISA

The coupling of an angular jitter into the interferometric phase readout is summarized under the term tilt-to-length (TTL) coupling. This noise is expected to be a major noise source in the intersatellite interferometry for the Laser Interferometer Space Antenna (LISA) space mission. Despite efforts to reduce it by satellite construction, some remaining TTL noise will need to be removed in postprocessing on Earth. Therefore, such a procedure needs to be developed and validated to ensure the success of the LISA mission. This paper shows a method to calibrate and subtract TTL noise that has no impact on LISA science operations. This solution relies on noise minimization and uses the differential wavefront sensing (DWS) measurements to estimate the TTL contribution. Our technique is applied after the laser frequency noise is suppressed via the time-delay interferometry (TDI) postprocessing algorithm. We use a simulation to show as a proof-of-principle that we can estimate the TTL coefficients to the required accuracy level based on the current design configuration of LISA. We then use these estimates to subtract the TTL noise, ensuring that any remaining TTL noise is below the current estimate of the other noise sources. We validate the procedure on simulated data for different operating scenarios. Our work shows that it is indeed possible to estimate the effect of TTL coupling and subtract it a posteriori from the TDI data streams.

Experimental study on the flow patterns and acoustic characteristics of surface piercing cylinders

The hydrodynamic characteristics and noise generated from flow around surface-piercing cylinders are a critical issue for many engineering applications. This article presents an experimental study of flow around a surface-piercing cylinder at Froude number 0.87 to 1.73. The bow wave height, wake pattern, air ventilation, and noise generated have been investigated extensively for different cylinders design such as circular and elliptical cylinders. The diameter of the circular and elliptical cylinders is 40 mm, and 53 mm, respectively. An image processing technique is applied to visualize the air entrainment and calculate the air volume fraction underwater. Due to the lack of experimental published data on the noise around the surface-piercing cylinder, a part of the results discussed the acoustic measurements. A hydrophone is used to study acoustic measurements. The result reveals that the wake region and the bow wave increases significantly as the Froude number increase, accompanied by an air cavity and vortex shedding region behind the circular cylinder, while there was less increment in the bow wave height and wake region as well as there was no air cavity for the case of an elliptical cylinder. The processed image indicated that the air volume fraction for the case of a circular cylinder is four-time higher compared to the elliptical cylinder at Froude number 1.73. Moreover, the results observed that the sound pressure level (SPL) increased as the Froude number increased in all frequency ranges. The sound pressure level behind the circular cylinder increased significantly in the frequency range <1000 Hz, while there was no increment in the SPL behind the elliptical cylinder. The major noise source is due to the air-ventilated cavity behind the cylinder. The outcome results of this study are an important reference for submarine mast designers and some other engineering applications.

Large Interferometer For Exoplanets (LIFE)

Context.One of the long-term goals of exoplanet science is the atmospheric characterization of dozens of small exoplanets in order to understand their diversity and search for habitable worlds and potential biosignatures. Achieving this goal requires a space mission of sufficient scale that can spatially separate the signals from exoplanets and their host stars and thus directly scrutinize the exoplanets and their atmospheres.Aims.We seek to quantify the exoplanet detection performance of a space-based mid-infrared (MIR) nulling interferometer that measures the thermal emission of exoplanets. We study the impact of various parameters and compare the performance with that of large single-aperture mission concepts that detect exoplanets in reflected light.Methods.We have developed an instrument simulator that considers all major astrophysical noise sources and coupled it with Monte Carlo simulations of a synthetic exoplanet population around main-sequence stars within 20 pc of the Sun. This allows us to quantify the number (and types) of exoplanets that our mission concept could detect. Considering single visits only, we discuss two different scenarios for distributing 2.5 yr of an initial search phase among the stellar targets. Different apertures sizes and wavelength ranges are investigated.Results.An interferometer consisting of four 2 m apertures working in the 4–18.5 μ.m wavelength range with a total instrument throughput of 5% could detect up to ≈550 exoplanets with radii between 0.5 and 6R⊕with an integratedS/N≥ 7. At least ≈160 of the detected exoplanets have radii ≤1.5R⊕. Depending on the observing scenario, ≈25–45 rocky exoplanets (objects with radii between 0.5 and 1.5R⊕) orbiting within the empirical habitable zone (eHZ) of their host stars are among the detections. With four 3.5 m apertures, the total number of detections can increase to up to ≈770, including ≈60–80 rocky eHZ planets. With four times 1 m apertures, the maximum detection yield is ≈315 exoplanets, including ≤20 rocky eHZ planets. The vast majority of small, temperate exoplanets are detected around M dwarfs. The impact of changing the wavelength range to 3–20 μm or 6–17 μm on the detection yield is negligible.Conclusions.A large space-based MIR nulling interferometer will be able to directly detect hundreds of small, nearby exoplanets, tens of which would be habitable world candidates. This shows that such a mission can compete with large single-aperture reflected light missions. Further increasing the number of habitable world candidates, in particular around solar-type stars, appears possible via the implementation of a multi-visit strategy during the search phase. The high median S/N of most of the detected planets will allow for first estimates of their radii and effective temperatures and will help prioritize the targets for a second mission phase to obtain high-S/N thermal emission spectra, leveraging the superior diagnostic power of the MIR regime compared to shorter wavelengths.

Increased signal-to-noise ratios within experimental field trials by regressing spatially distributed soil properties as principal components.

Environmental variability poses a major challenge to any field study. Researchers attempt to mitigate this challenge through replication. Thus, the ability to detect experimental signals is determined by the degree of replication and the amount of environmental variation, noise, within the experimental system. A major source of noise in field studies comes from the natural heterogeneity of soil properties which create microtreatments throughout the field. In addition, the variation within different soil properties is often nonrandomly distributed across a field. We explore this challenge through a sorghum field trial dataset with accompanying plant, microbiome, and soil property data. Diverse sorghum genotypes and two watering regimes were applied in a split-plot design. We describe a process of identifying, estimating, and controlling for the effects of spatially distributed soil properties on plant traits and microbial communities using minimal degrees of freedom. Importantly, this process provides a method with which sources of environmental variation in field data can be identified and adjusted, improving our ability to resolve effects of interest and to quantify subtle phenotypes.

Time–frequency characteristics of noise generated from different slat and flap geometrical configurations of the high-lift device

High-lift device installed on modern large aircraft is a major noise source during the approach and landing phases. For high-lift device, slat and flap parameters such as gap, overlap and deflection angle have strong effect on aerodynamic and aeroacoustic characteristics. However, the research about time–frequency characteristics of high-lift device noise affected by slat and flap parameters is lacking. This paper presents an investigation on 30P30N model to reveal the effect of different slat and flap geometrical configurations on the aeroacoustic time–frequency characteristics with experimental measurement and wavelet analysis. The results show that the multiple tones at small flap and slat deflection angles are mainly generated from the flap gap region. The time–frequency characteristic of the tones is satisfied with the amplitude modulation phenomenon, namely that the acoustic energy concentrates on the primary tone and the other tones are generated from the modulation process of the primary tone. While the multiple tones at large slat deflection angles are generated from the slat cove and slat gap regions. The time–frequency characteristic of the tones is satisfied with the mode switching phenomenon, namely that the dominant noise energy temporally switches from one mode to another in time and these multiple tones cannot coexist independent of one another.

Dynamic force measurement to assess NVH performance of electric motors

The electromagnetic (EM) force induced motor whine is a major noise source of hybrid and electric vehicles. Experimental quantification of dynamic EM force is highly desirable to assess the NVH performance of electric motors. However, it is difficult to measure EM forces directly on the stator teeth. This paper describes a new indirect method to measure the dynamic forces at stator mounting ear locations. First, high-precision tri-axial piezoelectric force ring sensors are selected and calibrated to measure dynamic forces under compressive mean loading. Next, special motor housings are designed and built to accommodate force sensors between the stator ears and the base mounting plate. Force sensors are then aligned with the stator circumferential directions to measure dynamic forces in radial, tangential and axial directions as a function of motor torque and speed. The new technology is successfully implemented for electric motors of GM's Spark and Bolt EVs. Measured dynamic forces correlate well with finite-element analytical results and show consistent trends with noise and vibration responses. This confirms the dynamic mounting force can be used as an effective and measurable indicator to optimize NVH designs for electric motors.

Study of Installation Effects on Automotive Cooling Fan Noise

&lt;div class="section abstract"&gt;&lt;div class="htmlview paragraph"&gt;Vehicle electrification is one of the biggest trends in the automotive industry. Without the presence of combustion engine, which is the main noise source on conventional vehicles, noise from other components becomes more perceivable; among these components, the cooling fan is one of the major noise sources, especially during battery charging. The design of cooling fan modules is usually carried out in the early stage before building prototype vehicles. Therefore, understanding the installation effects of the cooling fan on the radiated sound is essential to secure good customer satisfaction. In this study, three different measurement setups of cooling fans are carried out: free field, wall mounted, and in-vehicle measurement. Four cooling fan prototypes with different fan blade designs are used in each measurement. Correlations of these measurements are investigated through comparisons of the measurement results. The installation effects are identified through spectrum difference between free field and in-vehicle measurement. A spectral decomposition method is implemented to enable the separation of source strength and propagation effect in the results. One variable is introduced to represent the installation effects of vehicles tested in the present study.&lt;/div&gt;&lt;/div&gt;

Gut mucosa dissociation protocols influence cell type proportions and single-cell gene expression levels

Single-cell RNA sequencing (scRNA-seq) has revolutionized the study of the cellular landscape of organs. Most single-cell protocols require fresh material, which limits sample size per experiment, and consequently, introduces batch effects. This is especially true for samples acquired through complex medical procedures, such as intestinal mucosal biopsies. Moreover, the tissue dissociation procedure required for obtaining single cells is a major source of noise; different dissociation procedures applied to different compartments of the tissue induce artificial gene expression differences between cell subsets. To overcome these challenges, we have developed a one-step dissociation protocol and demonstrated its use on cryopreserved gut mucosal biopsies. Using flow cytometry and scRNA-seq analysis, we compared this one-step dissociation protocol with the current gold standard, two-step collagenase digestion, and an adaptation of a recently published alternative, three-step cold-active Bacillus licheniformus protease digestion. Both cell viability and cell type composition were comparable between the one-step and two-step collagenase dissociation, with the former being more time-efficient. The cold protease digestion resulted in equal cell viability, but better preserves the epithelial cell types. Consequently, to analyze the rarer cell types, such as glial cells, larger total biopsy cell numbers are required as input material. The multi-step protocols affected cell types spanning multiple compartments differently. In summary, we show that cryopreserved gut mucosal biopsies can be used to overcome the logistical challenges and batch effects in large scRNA-seq studies. Furthermore, we demonstrate that using cryopreserved biopsies digested using a one-step collagenase protocol enables large-scale scRNA-seq, FACS, organoid generation and intraepithelial lymphocyte expansion.

Impact of topography on attenuation of noise from a cement plant in a hilly terrain

The influence of hill topography on noise from industrial plants is scantly documented, despite the fact that the noise profiles can vary in plains and in hilly terrain. Significant noise data from a cement plant flanked by hills were collected and analyzed for its attenuation over space in the direction of the valley and across the hills. It was observed that the noise attenuation is not similar to that experienced in plains owing to interactions with the mountains. The overall effect has been modelled over different distances between the four sources of the noise and several monitoring stations. The analyzed noise data showed that the influence of the major source of noise is obvious, yet difficult to differentiate. An iterated weighted distance from the noise sources, proved to be a better estimate for distance while modelling the attenuation of the noise. A relationship between the equivalent noise levels during the day and night could also be established. The effect of relative altitude and slope could be modelled using nonlinear multivariate analysis and the response surfaces were obtained for minimum, maximum and average values of the variables. Noise shadow zones could be identified with noise contouring which reflects reduction in the noise levels on hind side of the hills. The impact of topography and possible interference could thus be defined in such hilly terrain. The information can be used to define the noise mitigation strategies for adjacent habitats and mitigation of human response. The findings of the paper can also be used by prospective plants in hilly areas.

Normalizing and denoising protein expression data from droplet-based single cell profiling

Multimodal single-cell profiling methods that measure protein expression with oligo-conjugated antibodies hold promise for comprehensive dissection of cellular heterogeneity, yet the resulting protein counts have substantial technical noise that can mask biological variations. Here we integrate experiments and computational analyses to reveal two major noise sources and develop a method called “dsb” (denoised and scaled by background) to normalize and denoise droplet-based protein expression data. We discover that protein-specific noise originates from unbound antibodies encapsulated during droplet generation; this noise can thus be accurately estimated and corrected by utilizing protein levels in empty droplets. We also find that isotype control antibodies and the background protein population average in each cell exhibit significant correlations across single cells, we thus use their shared variance to correct for cell-to-cell technical noise in each cell. We validate these findings by analyzing the performance of dsb in eight independent datasets spanning multiple technologies, including CITE-seq, ASAP-seq, and TEA-seq. Compared to existing normalization methods, our approach improves downstream analyses by better unmasking biologically meaningful cell populations. Our method is available as an open-source R package that interfaces easily with existing single cell software platforms such as Seurat, Bioconductor, and Scanpy and can be accessed at “dsb [https://cran.r-project.org/package=dsb]”.

Computational aeroacoustics of aerofoil leading edge noise using the volume penalization-based immersed boundary methods

Broadband noise due to the turbulence-aerofoil interaction, which is also called the leading edge noise, is one of the major noise sources of aircraft (including the engine). To study the noise properties numerically is a popular approach with the increasing power of computers. Conventional approaches of using body-fitted grids at the boundaries would be convoluted due to the complex geometries, which can constrain the efficiency of parametric studies. A promising approach to tackle this issue is to use the immersed boundary method (IBM). Among various IBM variants, the volume penalization (VP) approach employs a masking function to identify the immersed solid boundary, and continuous forcing terms are added to the original flow governing equations to account for the boundary conditions. It is, therefore, efficient and easy to implement into the existing computational aeroacoustics solvers. In this work, the VP-based IBM is used to simulate the leading edge noise by combining with the advanced synthetic turbulence method. The simulations are conducted for both the isolated aerofoils and cascade, and the results are compared with the well-validated body-fitted grid solutions. The viscosity effect is also highlighted by comparing the results obtained by solving both Euler and Navier–Stokes equations.

우주과학임무를 위한 큐브위성 자기장 청결도 분석

CubeSat is a satellite platform that is widely used not only for earth observation but also for space exploration. CubeSat is also used in magnetic field investigation missions to observe space physics phenomena with various shape configurations of magnetometer instrument unit. In case of magnetic field measurement, the magnetometer instrument should be far away from the satellite body to minimize the magnetic disturbances from satellites. But the accommodation setting of the magnetometer instrument is limited due to the volume constraint of small satellites like a CubeSat. In this paper, we investigated that the magnetic field interference generated by the cube satellite was analyzed how much it can affect the reliability of magnetic field measurement. For this analysis, we used a reaction wheel and Torque rods which have relatively high-power consumption as major noise sources. The magnetic dipole moment of these parts was derived by the data sheet of the manufacturer. We have been confirmed that the effect of the residual moment of the magnetic torque located in the middle of the 3U cube satellite can reach 36,000 nT from the outermost end of the body of the CubeSat in a space without an external magnetic field. In the case of accurate magnetic field measurements of less than 1 nT, we found that the magnetometer should be at least 0.6 m away from the CubeSat body. We expect that this analysis method will be an important role of a magnetic cleanliness analysis when designing a CubeSat to carry out a magnetic field measurement.

Sources of noise and their effects on nurses in intensive care units: A cross sectional study

BackgroundNoise is a serious threat to the health of people. In Intensive Care Units (ICU), the higher level of noise may negatively affect the health of the patients and health care staff. ObjectivesTo determine the sources of noise and the related adverse effects from the ICU nurses’ viewpoints. MethodsThe study sample included all nurses (148) working in ICUs. The data collection tool was a three-section questionnaire. The first section was related to personal- occupational characteristics. The second part evaluated internal and external noise sources from the nurses' viewpoints. The third section assessed the effect of noise on four domains: physiology, emotions, subjective perception, and performance. The data were analyzed by SPSS version 22, using descriptive and inferential statistics. ResultsThe results showed that the major internal sources of noise were monitoring alarms and ventilators (61.5%).The highest and lowest mean ± SD of the scores about the effect of noise on the study domains were related to physiology (16.1 ± 4.8) and performance (14.9 ± 5.25). The three domains' scores (subjective perception, emotions, physiology) had significant relationship with the bed occupancy rate, the type of ICU, and the number of beds (P < 0.05). Also, the performance domain's scores had a significant relationship with work experience, bed occupancy rate, and shift type (P < 0.05). ConclusionsSince ambient noise is a threat to health and disturbs the patients and ICU staff, we believe that proper strategies should be designed to reduce its levels.

Measuring speed of vessels operating around endangered southern resident killer whales (Orcinus orca) in Salish Sea critical habitat

Motorized vessels are a major source of anthropogenic noise and can have adverse effects on species relying on sound for communication and feeding. Monitoring noise levels received by endangered southern resident killer whales (SRKWs) requires knowing the number, distance, and speed of surrounding vessels, including small boats that do not have Automatic Identification Systems (AIS). A method for estimating their speed is required to predict received noise levels and compliance with vessel regulations. We compared theodolite and photogrammetry methods to estimate the number, distance, and speed of vessels in SRKW Salish Sea summertime critical habitat. By treating AIS as “truth”, we found photogrammetry-derived ranges and speeds were more variable than theodolite estimates. Error in photogrammetry-derived speeds increased with range. Overall, we found time saved in the field using photogrammetry was more than offset by long analysis time. Theodolite data were relatively easy to collect, and produced accurate and precise results.

Investigating the impact of scatter correction on Centiloid

AbstractBackgroundCentiloid (CL) is a semiquantitative measure of amyloid‐β burden based on the ratio between neo‐cortical target region and the whole cerebellum. Photon scatter is one of the major sources of noise in PET data. Scatter correction methods are very different across PET cameras. In this study, we investigate how scatter correction affects the CL for inter/intra‐cameras by comparing PET images with/without scatter correction.Method203 subjects (Siemens mCT Biography (N=109), Philips Gemini TF 64 (N=94)) from the AIBL study were scanned with 18F‐NAV6240. All PET images were reconstructed off‐line with scatter correction enabled and then disabled. All images were processed by CapAIBL to generate CL values. The ΔCL, which was calculated as the difference between the scatter corrected CL and non‐scatter corrected CL, was investigated to quantify the impact of scatter correction. For the intra‐camera comparison, all subjects were categorised in three groups based on the head tilt along anteroposterior axis compared to the MNI‐152 template. For inter‐camera comparison, the head tilt angle was included as covariate into an ANOVA. Hierarchical linear regressions that included head tilt and camera models were used as covariates to investigate their effect on CL.ResultFigure 1 shows that scatter correction has a larger impact on the cerebellum cortex than in neocortex. Figure 2 shows that scatter correction depends on the head position, and it has more impact on subjects with higher CL for both cameras. Figure 3 presents that scatter corrections from two different cameras have different impact on CL values. Both head tilt and camera model had an impact on the scatter correction with (F=19.5, p=1.67e‐5) and (F=109.4, p=1.1e‐20), respectively. The b coefficients were 0.38CL/degree for head tilt and 8.2CL for the camera model, where more scatter is corrected on the Siemens CT than on the Philips Gemini TF.ConclusionOur results show that difference in scatter correction from different cameras have a significant impact on CL, it is yet to be known whether it is caused by hardware difference or software difference. Additional investigations using test‐retest data is needed to further characterize the real impact of scatter correction on Centiloid.

Temporal Variability in Acoustic Behavior of Snapping Shrimp in the East China Sea and Its Correlation With Ocean Environments

The snapping shrimp sound is known to be a major biological noise source of ocean soundscapes in coastal shallow waters of low and mid-latitudes where sunlight reaches. Several studies have been conducted to understand the activity of snapping shrimp through comparison with surrounding environmental factors. In this paper, we report the analysis of the sound produced by snapping shrimp inhabiting an area where sunlight rarely reaches. The acoustic measurements were taken in May 2015 using two 16-channel vertical line arrays (VLAs) moored at a depth of about 100 m, located ∼100 km southwest of Jeju Island, South Korea, as part of the Shallow-water Acoustic Variability Experiment (SAVEX-15). During the experiment, the underwater soundscape was dominated by the broadband impulsive snapping shrimp noise, which is notable considering that snapping shrimp are commonly observed at very shallow depths of tens of meters or less where sunlight can easily reach. To extract snapping events in the ambient noise data, an envelope correlation combined with an amplitude threshold detection algorithm were applied, and then the sea surface-bounced path was filtered out using a kurtosis value of the waveform to avoid double-counting in snap rate estimates. The analysis of the ambient noise data received for 5 consecutive days indicated that the snap rate fluctuated with a strong one-quarter-diurnal variation between 200 and 1,200 snaps per minute, which is distinguished from the periodicity of the snap rate reported in the euphotic zone. The temporal variation in the snap rate is compared with several environmental factors such as water temperature, tidal level, and current speed. It is found that the snap rate has a significant correlation with the current speed, suggesting that snapping shrimp living in the area with little sunlight might change their snapping behavior in response to changes in current speed.

Acoustic Sensing and Noise Identification of a Heating, Ventilation and Air Conditioning Unit: Industrial Case Study

Reducing the noise and improving the sound quality of vehicles’ interior space is one of the challenges to enhance passengers’ experience. This is an ever-growing issue as entirely electric cars are becoming commonplace, making previously unnoticed noise a significant problem. Heating, Ventilation and Air Conditioning (HVAC) units are a major noise source in a vehicle’s interior space, yet automotive manufacturers only give a maximum dB specification to HVAC unit manufactures. Problematic noise is only typically identified once the unit is within the vehicle at the late stages of a project. Psychoacoustics is the study of human perception to sound, allowing unpleasant noise to be identified within recorded data. Within this study, an industrial prototype HVAC unit was analysed using a 96-channel acoustic camera capable of isolating and locating noise sources from the unit using beamforming. In addition to identifying the location of noise sources, several psychoacoustic metrics were used, such as sharpness and loudness, to identify undesirable noise within an extensive data set due to the vast range of test configurations. Testing was conducted to analyse the unit. Within the initial testing, an ‘annoying’ sound was identified at a particular motor RPM, and this was located using the camera to an area which indicated that it was a result of structural resonance. In addition, present was a high-frequency source which could not be located accurately. The results of this testing enable modifications to the unit to be made early in its’ development, either structurally to alter the resonance of the unit or within the settings to ensure certain RPMs are avoided.

A Computational Study on the Aeroacoustics of a Multi-Rotor Unmanned Aerial System

The noise generated by a quadrotor biplane unmanned aerial system (UAS) is studied computationally for various conditions in terms of the UAS pitch angle, propellers rotating velocity (RPM), and the UAS speed to understand the physics involved in its aeroacoustics and structure-borne noise. The k-ω SST turbulence model and Ffowcs Williams-Hawkings equations are used to solve the flow and acoustics fields, respectively. The sound pressure level is measured using a circular array of microphones positioned around the UAS, as well as at specific locations on its structure. The local flow is studied to detect the noise sources and evaluate the pressure fluctuation on the UAS surface. This study found that the UAS noise increases with pitch angle and the propellers’ rotating velocity, but it shows an irregular trend with the vehicle speed. The major source of the UAS noise is from its propellers and their interactions with each other at small pitch angle. The propeller and CRC-3 structure interaction contributes to the noise at large pitch angle. The results also showed that the propellers and structure of the UAS impose unsteadiness on each other through a two-way mechanism, resulting in structure-born noises which depend on the propeller RPM, velocity and pitch angle.

Aerodynamic design and acoustic effect study of key geometric parameters of a sirocco fan

A sirocco fan (forward-curved centrifugal fan), including impeller blades and volute, is designed, and the empirical value ranges of several significant design parameters are discussed and summarized fromthe perspective of both aerodynamics and practical structure. Unsteady-flow numerical simulation and radiated sound-field calculation by indirect boundary element method are combined to evaluate its aerodynamic and acoustic performances. Both the discrete noise source from the rotating impeller and broadband noise source from the volute are considered. Obvious flow separation occurs in the flow passage of impeller blades due to large angle of attack, and the tongue region is the major noise source area due to the small impeller-tongue gap. Therefore, parametric studies for blade installation angle and impeller-tongue gap are performed. Analyses of flow- and sound-field indicate that appropriate reduction of blade geometry incidence angle weakens the flow separation, thereby improving both the aerodynamic and acoustic performances, and reasonable increase of the impeller-tongue gap has a remarkable noise reduction effect for the major noise source area near the volute tongue. The optimized sirocco fan meets the requirement of the industrial project, i.e., the far-field A-weighted sound power level lower than 64.0 dB(A), and achieves larger volume flow rate and total pressure rise. The results also imply that fast steady-flow numerical simulation result is indicative of the acoustic performance to some extent if the acoustic evaluation is urgent. Furthermore, optimization of the key structural parameters in the stage of design is preferable in practical engineering, instead of taking follow-up noise reduction measures.