Using a hearing protective device, feedback from the surroundings is of importance. Three aspects to be considered is the ability to communicate orally, the possibility to localize sound sources and to obtain a natural impression of the sounding environment. This could only be achieved by using a protective device that allow acoustic feedback, typically by a pair of microphones attached to the cup of each ear. The microphone signal is fed via an amplifier and an electronic compressor, that limit the amplitude of the signal fed to the loud speakers inside the cups. Typical problems with this type of solution are that the signals received by the two ears are distorted so much that sound localisation is difficult and that the sound is perceived unnatural. The objective of the project is to optimise the cup geometry especially where the microphones are mounted, and by that improve sound localisation and minimise the amplification of non-important weak sounds like the foot step of the user

Summary form only given. A complex sound source consists of several partial sound sources that all contribute to the total sound pressure. A method to separate these partial sound sources into separate time histories is based on inverse filtering of reciprocally measured transfer functions. The transfer functions are measured reciprocally between a number of fictitious monopoles on each partial source and measurement points distributed around the sound source. The method is divided into 5 steps: recording of sound pressure signals, measurement of transfer function, calculation of source strength matrix, calculation of filters and filtering of the recorded sound pressure signals. Correct estimations of the transfer functions are critical for inverse methods to work satisfactory. Normally the transfer functions in this case of studies are calculated as H1 because of the noise contribution to the responses. However, it has been suggested that inverse methods could benefit of using H2 instead. The objective of this investigation is to analyze the effect of selecting either H1 or H2 for the calculation of the transfer functions in case of auralization of separated time histories. For the experiments a complex sound source consisting of two separate cylinder heads with valve covers have been used. Each cylinder head with valve cover was treated as a partial source. The two partial sources were excited with two uncorrelated signals that could be controlled individually. By that, listening tests could be used to verify the authenticity of the separated source signals depending of the transfer functions were estimated as H1 or H2

Modern telecommunication services generally use digital speech encoding. Speech encoding degrades the audio with compression and filters to make the data transmission more efficient. To keep conversations and on-line meetings productive and creative it is important that these digital services do not increase the cognitive load. Measuring effects on working memory is one way to estimate cognitive load of the listener. A test with 25 participants was performed to investigate the effects of using the AMR-NB codec, a standardized codec for mobile communication. The memory performance for spoken 12-word lists was measured and AMR-NB encoded speech was compared with unprocessed speech (LPCM 16 bit, 44.1 kHz). A within-subject analysis showed 9% lower recall rate for the AMR-NB coded speech.

Pictures that demonstrate physical phenomena are important in science, so also in musical acoustics. In optics, interference, diffraction and polarization phenomena are for instance often pictured in text books. Phase contrast methods are used in microscopy to visualize transparent objects. Such methods have numerous applications in medicine and biology. Shadowgraph, schlieren and different kinds of classical interferometry setups are used in fluid mechanics to study laminar flow, turbulence, convection, subsonic and supersonic flow, shock waves etc. Propagating sound fields often accompany supersonic flow and shock waves. Also transparent object fields like sound and temperature fields can be pictured using optical measuring methods. Merits of these methods are that they are contactless, nondisturbing and wholefield methods. In this paper, some modern optical methods are presented that has the sensitivity and spatial resolution needed to visualize and measure sound fields in musical acoustics. They are computerized, all-electronic methods that present pictures but also give quantitative measures. Harmonic vibrations, standing waves, repetitive sequences and transient wave propagation will be addressed. TV holography, pulsed TV holography and scanning laser Doppler vibrometry (LDV), or scanning vibrometry will be discussed. Speckle photography and correlation methods like digital speckle photography (DSP) and particle image velocimetry (PIV) will also be shortly presented

To better understand the complex acoustic behaviour of lightweight building structures both experimental and theoretical approaches are necessary. Within the theoretical approach developing theoretical models is of great importance. The aim here is to further develop an existing method to predict the impact sound pressure level in a receiving room for a coupled floor structure where floor and ceiling are rigidly connected by beams. A theoretical model for predicting the impact sound level for a decoupled floor structure, which has no rigid mechanical connections between the floor and the ceiling, is developed. An analytical method has been implemented, where a spatial Fourier transform method as well as the Poisson's sum formula is applied to model transformed plate displacements. Radiated sound power was calculated from these displacements and normalized sound pressure levels were calculated in one-third octave frequency bands. The predicted results from the model are compared with the results from the experiments on the decoupled floor-ceiling construction. The results gave agreements in line with comparisons regarding previous model. The effect of introducing beam-plate moment in the model is studied and is found to be dependent on frequency, showing significant improvement in predicting impact sound level at high frequency region.

This study presents a qualitative method for collecting and analysing data to describe audio and video quality. Used in the social sciences, arts, and humanities, this approach relies on phenomenology and hermeneutics and uses interviews and questionnaires to assess the audio and video quality of master classes in classical music taught via the Internet. Although this study is only exploratory, it provides evidence that the method could successfully be used to gather descriptions of perceived qualities.

In the past, musical instruments were developed over long periods of time by skilled craftsmen. Today, most instruments are mass-produced. Design of musical instruments as mass-produced products requires using strategies which make it easier to identify customer needs and develop exact specifications. To develop useful specifications it is necessary to convert general descriptions into something which can be commonly understood and also be interpretable in terms of acoustic metrics. In this study, methods for analysis and specification of steady state parts of alto saxophone sounds were developed. Saxophonists' use of verbal descriptions of saxophone sounds was investigated. Sound stimuli were binaurally recorded. Judgements upon perceived qualities were made by saxophonists and non-saxophonists using the method of verbal attribute magnitude estimation. Perceptual dimensions were identified using principal component analysis of listening test data. Three prominent dimensions were found and described using the verbal attributes: 1) warm/soft, 2) back vowel analogues and 3) sharp/rough. The perceptual dimensions were modelled as linear functions of acoustic metrics. The results were validated through listening tests with new subjects and new stimuli. Based on the findings, the method was seen as an approach which can enhance the musical instrument design process.

How do the walls of an open organ pipe vibrate when blown? Two geometrically similar open organ pipes are made of different alloys and tooled in different ways. Using a scanning laser Doppler vibrometer the operational deflection shapes (forced modes of vibration) for the first three harmonic partials of the blown pipes are measured. The upper lip is further investigated for the five first harmonic partials. The results are compared and related to the sound intensity distribution from the pipes. This comparison shows that the vibration modes of the structure are dependent upon the material of the pipes. Both the amplitude and the shape of the vibration differ between the pipes. It is found that the vibration amplitude is low for the fifth harmonic partial. For this partial the sound intensity emitted from the mouth also is low.

In this paper the boundary element method (BEM) is used to determine acoustic-related quantities in open domains from vibrating structures. Two different types of structures have been analysed, a sphere and an engine transmission cover. The analysed acoustical quantities are pressure amplitude and pressure and intensity amplitude respectively. The numerical results were compared with the analytical and experimental results. In both cases, the sphere and the transmission cover, the input to the BEM program is the normal velocity of the structure surface. The analysed frequency range was in the case of the sphere 100–5000 Hz and a good agreement between numerical and analytical results was obtained up to frequency 3500 Hz. In the engine transmission cover case, the analysed frequency range was 434–3552 Hz with an overall good agreement between numerical and experimental results in the frequency range of 644–1848 Hz.

This investigation had two goals: first was the evaluation of noise annoyance in seven control rooms based on listening tests and psychoacoustical parameters; second was the comparison of four hearing protective devices in terms of noise annoyance while exposed to loud sounds from a steel plant. Binaural recording technique was used for recording and playback of the sound signals. A total of 48 subjects participated in the first experiment and 8 subjects participated in the second experiment. They evaluated noise annoyance on an 11 point scale. In the second experiment four hearing protective devices were tested: two types of ear cups, slow-recovery foam ear plugs and custom modeled ear plugs. Loudness and roughness were the most significant contributors to noise annoyance in control rooms. Interaction between loudness, sharpness, roughness, and tonality were statistically significant. Noise annoyance with ear cups was lower than with ear plugs. However, this effect was dependent on gender. Ear cups reduced noise annoyance for male subjects more, than for female subjects