Vibrotactile enhancement of musical engagement.

Sound is sensed by the ear but can also be felt on the skin, by means of vibrotactile stimulation. Only little research has addressed perceptual implications of vibrotactile stimulation in the realm of music. Here, we studied which perceptual dimensions of music listening are affected by vibrotactile stimulation and whether the spatial segregation of vibrations improves vibrotactile stimulation. Forty-one listeners were presented with vibrotactile stimuli via a chair's surfaces (left and right arm rests, back rest, seat) in addition to music presented over headphones. Vibrations for each surface were derived from individual tracks of the music (multi condition) or conjointly by a mono-rendering, in addition to incongruent and headphones-only conditions. Listeners evaluated unknown music from popular genres according to valence, arousal, groove, the feeling of being part of a live performance, the feeling of being part of the music, and liking. Results indicated that the multi- and mono vibration conditions robustly enhanced the nature of the musical experience compared to listening via headphones alone. Vibrotactile enhancement was strong in the latent dimension of 'musical engagement', encompassing the sense of being a part of the music, arousal, and groove. These findings highlight the potential of vibrotactile cues for creating intensive musical experiences.

The influence of the reference level on loudness and preference judgements for spectrally manipulated fan sounds.

Fan sounds are often quantified using A-weighted sound pressure levels, silently acknowledging their limitations to fully capture the perceived unpleasantness. To overcome this limitation, level adjustments are a way to quantify the subjective preference of spectrally different sounds in listening experiments by adjusting the level of a test sound until it is equally preferred to a fixed reference sound. Since equal loudness contours differ, depending on the overall level, level adjustments might vary for different levels of the reference sound. This study aims to quantify the effects of spectral manipulations on level adjustments for loudness and preference judgements at reference sound pressure levels of either 45, 60, or 75 dB(A). Level adjustments of up to 12 dB were measured to make the stimuli equally preferred to the reference, particularly for sounds with prominent high-frequency components. The loudness and preference judgements were closely linked with each other, but an offset of about 3.5 dB at a reference level of 45 dB(A) indicates that equal loudness is not synonymous with equal preference. A linear regression model to predict level adjustments based on the reference level and an index reflecting the ratio of mid- to high-frequency loudness explains 73% of the variance.

Loudness and short-term annoyance of sonic boom signatures at low levels.

Supersonic aircraft produce a sonic boom when flying faster than the speed of sound. To rule out detrimental effects for inhabitants of overflown areas, civil supersonic flights (like the Concorde) were only allowed to fly at supersonic speed when over water. Due to the progress in aircraft design, the supersonic boom may be reduced considerably in the future. In this study, listening tests were carried out with a variety of low boom simulations and conventional sonic boom signatures in a similar level range. Participants rated the loudness and the short-term annoyance of 24 sonic boom signals, which differed in terms of the signature shape and maximum pressure but were confined to a range of A-weighted sound exposure levels around 60 dB(A). The results showed main effects of signature and relative level variation as well as an interaction of the two. Correlation coefficients between the ratings and sound exposure levels were highest for A-weighted sound exposure levels compared to other frequency weightings. Contrary to our expectations, the provision of background information about the nature of the presented sound sources had no statistically significant influence on the ratings.

Determination of preference-equivalent levels for fan noise and their prediction by indices based on specific loudness patterns.

In a previous study by the authors, two indices were identified as appropriate descriptors for perceptual dimensions of fan noise. The index Nlow describes the amount of low-frequency loudness relative to the overall loudness. The index Nratio represents the ratio between the amount of loudness resulting from mid-frequency content and that from high frequencies. The aim of this study is to quantify how variations in these two indices affect subjects' preferences and loudness judgments. In listening experiments, fan noise signals were adjusted separately to equal loudness and equal preference compared to a common reference sound by varying their level in an adaptive procedure. The fan noises used in the listening tests consisted of 11 typical signals from three major groups of fan sounds from the earlier study and 18 signals that were parametrically varied in terms of the two indices. Reductions in A-weighted sound pressure level of up to 15 dB were necessary to make unpleasant fan sounds equally preferred as the fixed reference sound. A regression model based on the index Nratio explains 81% of the variation in the evaluation data with a root-mean-squared error of 2.53 dB.

Perceptual space, pleasantness and periodicity of multi-tone sounds.

Technical sounds often contain several tonal components, forming a multi-tone sound. The present study investigates the perception of multi-tone sounds consisting of two harmonic complexes with different fundamental frequencies and combination tones with frequencies that are equal to the sum of multiple integers of the two fundamentals. The experimental parameter is the ratio between the two fundamental frequencies ρ. A total of 15 synthetic multi-tone sounds are rated by 37 participants. In the first experiment, the perceptual space is assessed based on 16 adjective scales using categorical scaling. The resulting perceptual space has the four dimensions (i) pleasant, (ii) power, (iii) temporal structure, and (iv) spectral content of the sounds. In the second experiment, the pleasantness is measured with a paired comparison test. The data consistently show that sounds based on ratios of small integers (e.g., ρ=4:3) are significantly less pleasant than sounds with ratios based on large integers which were constructed by a slight detuning from a ratio of small integers. The repetition rate derived from an autocorrelation analysis of the stimuli turns out to be a good predictor of the (un-)pleasantness sensation.