Psychoacoustic Analysis of Vacuum Cleaner Noise

Vacuum cleaners are one of the most widely used household appliances associated with unpleasant noises. Previous studies have indicated the severity of loud vacuum cleaner noise and its impact on the users nearby. The standalone quantified measurements of the generated noise are not sufficient for properly characterizing vacuum cleaners. Human perception should also be included for a better assessment of the quality of sound. A hybrid approach such as psychoacoustics analysis, which comprises subjective and objective evaluations of sounds, has recently been widely used. This paper focuses on the experimental assessment of vacuum cleaner noise and evaluates their psychoacoustical matrices. Three vacuum cleaners with different specifications have been selected as test candidates, and their sound qualities have been analyzed. Statistical analysis, ANOVA, has been performed in order to investigate the effectiveness of individual psychoacoustic metrics.

Experimental investigation on acoustics and efficiency of rotor configurations for electric aerial vehicles

Aerial vehicles based on distributed electric propulsion systems have gained great interest. Their rotors however create loud and annoying sound, what obstructs market success. Variations in rotor configuration can be observed on emerging concepts, whereby the main varied parameters are blade radius, number of blades and blade distribution. The focus of this paper is to identify how these parameters can be chosen to optimize efficiency and acoustics, including psychoacoustic metrics and sound quality of single rotors while hovering. Results from experimental investigations done in a hover-test-bench are presented. Rectangular, symmetric blades are used. Experiments are done varying blade radius (61mm to 126 mm), number of blades (2 to 8) and blade distribution (equal and unequal angles). Acoustic measurements are analyzed regarding microphone position, sound pressure level, spectral characteristics, psychoacoustic metrics and selected sound quality models. Results show, that variations in blade radius, number of blades and blade distribution can improve efficiency and acoustics. Influence of these parameters on the acoustic signature at constant rotational speed and at constant thrust is discussed. Conclusions for optimized rotor design at aerial vehicles are derived and supplemented by resulting boundary conditions like building space and weight.

The Study of Sound Quality for Car Compressor

As cars become more and more quiet the sound quality of rotary components such as car compressor becomes more important in the customer’s subjective perception of passenger car quality. This needs a new evaluation method which is not only the traditional method like sound pressure level but also Psychoacoustic Metrics to focus the specification of component sounds. This paper on one hand analyzed one car’s abnormal noise reason through the tests, found the main problem frequency band of the compressor, and on the other hand studied the compressor’s psychoacoustic metrics. In this paper the countermeasure of solving this problem was also given, and then noise level and psychoacoustic parameters are compared. Both objective evaluation and subjective evaluation showed that the compressor with the solution not only reduced the sound pressure level, but also improved the car sound quality greatly.

Psychoacoustic modelling of vehicle side mirror power-fold actuator noise characteristics

A study of vehicle side mirror power-fold actuator noise characteristic was undertaken, which seeks to correlate subjective evaluation with objective measurements as a basis for development of a product sound quality control algorithm. Psychoacoustic metrics were extracted from the product sound measurements and analysed for manufacturing quality assessment. Two approaches were explored in this study; one is a multiple metric sequential pass-through gate approach and the other is the least square fit regression approach, where measured relevant psychoacoustic metrics are modelled against subjective rating data provided by product sound quality evaluation experts. The ‘gate’ approach using sound pressure level, roughness, and tonality was successfully implemented to segregate bad power-fold actuators from good ones in terms of sound quality. A non-linear, two metric regression algorithm assessing what is a ‘good’ or a ‘bad’ actuator, was then developed and validated through comparison with a linear eight metric regression algorithm. Based on correlation of objective measurement and subjective evaluation results for given product samples, the diagnostic methodology developed in this research is applicable to other products for noise diagnostics and quality control.

Use of Psychoacoustic Metrics for the Analysis of Next Generation Computer Graphic Card Noise

The continuing challenge to deliver performance improvements in computer graphic cards has long since progressed to the point of requiring finned, passive, cooling devices to dissipate the heat generated by the graphics processing unit (GPU). The heat flux generated by further improvements now exceeds that dissipation capacity so that passive cooling can no longer provide adequate cooling the GPU. The dissipation rates required by the latest generation of designs can be delivered by forced air cooling of finned heat sinks. The concurrent challenge to the industry is to provide this cooling while minimizing the noise generated by these cooling fans. A significant aspect associate with this problem is missed if one only considers the problem to be a one-dimensional sound level issue. From a consumer’s perspective, the perceived quality of the noise emitted takes precedence over what traditional acoustical analysis techniques of this fan noise may imply. Here, psychoacoustic or sound quality metrics, may be a more applicable analysis tool as it provides the quantification of these qualitative human impressions. The present study investigates the validity of using several psychoacoustic metrics for the analysis of fan cooled computer graphics card noise. Using experimentally measured fan noise from three different cooling fan designs, a sound quality analysis was performed using loudness, sharpness, roughness, fluctuation strength, prominent tone and articulation index. A discussion and comparison of measured results using traditional analysis techniques is also included. It was found that some of the metrics proved more useful than others as an analysis tool for this specific noise source. A discussion of the applicability of the various sound quality metrics along with justifications is presented.

Effect of Next Generation Computer Graphic Card Blower Fan Speed on Thermal Performance and Acoustic Noise With Psychoacoustic Metrics

Graphic Processor Units (GPUs) on the latest models of computer graphic cards generate significant amounts of heat. In fact, the required dissipation rate is so large that cooling fans mounted on heat-sinks must be used to maintain satisfactory GPU temperatures. The packaging of these fans is small and similar designs have been used for cooling of electronic packaging for decades. The appropriate application of these fans as well as their optimal design for minimal noise generation and maximum air movement has not kept pace with that of large industrial sized fans. Where space limitations allow and heat transfer requirements dictate, blower type fans are implemented because they are capable of delivering relatively high flow rates in high impedance environments when they are compared to more traditional axial flow fans. The operation of these blower fans, particularly at high speeds, results in the generation of noise which is experienced by the user. Both computer manufacturers and consumers alike have deemed this noise to be excessive and annoying. The fan model predictions and the operational reality of the higher fan speeds needed to deliver increased air flow both lead to the reality of higher noise levels. The purpose of this study was to experimentally investigate the realized thermal and acoustic performance of a blower style fan-sink mounted on an advanced graphics port (AGP) card. The goal of this investigation was to determine what thermal benefits of higher flow rate are realized by the blower fan at the expense of increased noise emissions. The experimental results of thermal measurement results spanning the operating speed of the fan are presented and accompanied by the noise data. These data include both traditional acoustic analysis techniques using sound pressure and power level measurements as well as psychoacoustic metrics. The result of the thermal testing suggests that the rate of improvement in thermal performance decreases as the blower fan speed increases. As expected, an increase in noise level was also observed. Of particular interest were the results of the psychoacoustic analysis which indicate a similar detrimental effect with increased fan speed for some metrics, while other metrics indicate no change across the operating speed range of the blower fan.