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In this paper we present a metric that predicts differences in perceptual sharpness from physical parameters extracted from CCD camera recordings of sine-grating and step-profile test images. Sharpness differences were induced by using five different high-end television sets to display natural color images as well as by using blurred versions of these images. The metric is a two-step model that uses the perceptual strengths of three sharpness-related attributes on an intermediate level between the physical parameters and perceptual sharpness. The data obtained from category scaling experiments indicate that perceptual strength of sharpness is a linear combination of the perceptual strengths of the attributes detail rendering and contour rendering. It was found that differences in detail rendering correlate with differences in modulation depth of the sine gratings and that differences in contour rendering can be explained from the slope and overshoot parameters of the step-profiles.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

A single loudspeaker with frequency-dependent directivity characteristics, positioned in a room of normal size with frequency-dependent absorption coefficients of the room surfaces, has been simulated using an electroacoustic setup. The model included the direct sound, seventeen individual reflections and the reverberant field. The threshold of detection, and just-noticeable differences for an increase in level were measured for individual reflections. The results have confirmed that the first-order floor reflection is likely to contribute individually to the timbre of reproduced noise. However, for a speech signal none of the investigated reflections will contribute individually to the timbre. It is suggested that the threshold of detection is determined by the spectral changes in the dominant frequency range of 500 Hz to 2 kHz. For increases in the level of individual reflections, the most likely to be audible is the first-order floor reflection, for speech and noise. For a noise signal, additional reflections from the wall to the left and behind the listener also belong to this group.

This paper reports some of the influences of individual reflections on the timbre of reproduced sound. A single loudspeaker with frequency-independent directivity characteristics, positioned in a listening room of normal size with frequency-independent absorption coefficients of the room surfaces, has been simulated using an electroacoustic setup. The model included the direct sound, 17 individual reflections, and the reverberant field. The threshold of detection and just-noticeable differences for an increase in level were measured for individual reflections using eight subjects for noise and speech. The results have shown that the first-order floor and ceiling reflections are likely to individually contribute to the timbre of reproduced speech. For a noise signal, additional reflections from the left sidewall will contribute individually. The level of the reverberant field has been found to have an effect on the contribution of the individual reflections. An increase in the level of individual reflections are most likely to be audible for the first-order floor and ceiling reflections, and certain reflections from the sidewalls.

Audio systems and recordings are optimized for listening at the ’sweet spot’, but how well do they work elsewhere? An acoustic-perceptual model has been developed that simulates sound reproduction in a variety of formats, including mono, two-channel stereo, five-channel surround and wavefield synthesis. A virtual listener placed anywhere in the listening area is used to extract binaural signals, and hence interaural cues to the spatial attributes of the soundfield. Using subjectively-validated models of spatial sound perception, we can predict the way that human listeners would perceive these attributes, such as the direction (azimuth) and width of a phantom source. Results will be presented across the listening area for different source signals, sound scenes and reproduction systems, illustrating their spatial fidelity in perceptual terms. Future work investigates the effects of typical reproduction degradations.

Perceived sharpness is investigated for computer monitor tube (CMT) as well as for television tube (TVT) applications in a number of subjective evaluations using a test pattern and natural images blurred by Gaussian filters. For CMT applications, the visibility of differences in perceived sharpness is determined based on a simple black-and-white test pattern. This pattern is either blurred in the horizontal direction only or in both the horizontal and vertical directions. Subjective evaluations demonstrate that the perceived sharpness is related to the diagonal step response, determined from the horizontal and vertical step responses measured at the black-white transitions. For TVT applications, perceived sharpness is evaluated in three additional experiments, using mainly natural images and trained as well as inexperienced observers. For these experiments too, the diagonal step response describes the decrease in perceived sharpness for an increased degree of blurring very accurately.

This paper reports on the influence of individual reflections on the auditory localization of a loudspeaker in a small room. Two previous papers [J. Acoust. Soc. Am. 97, 1717–1726 (1995); ibid. (in press)] have reported on the influence of individual reflections on timbre of reproduced sound. The sound field produced by a single loudspeaker positioned in a normal listening room has been simulated using an electroacoustical setup. The setup models the direct sound, 17 individual reflections, and the reverberant field. The threshold of detection was measured using the method of adjustment for five reflections using three subjects for noise and speech. The thresholds have been measured for two simulated situations: (1) A loudspeaker with frequency‐independent directivity characteristics and frequency‐independent absorption coefficients of the room surfaces and (2) a loudspeaker with directivity according to a standard two‐way system and absorption coefficients according to real materials. The results have shown that subjects can reliably distinguish between timbre and localization, that the spectrum level above 2 kHz for individual reflections determines their influence on the localization of the main source, and that only the first‐order floor reflection will contribute to localization of the main source. a)Present address: Bang and Olufsen A/S, Peter Bangs Vej 15, DK‐7600 Struer, Denmark.

ARCHIMEDES is a psychoacoustics research project, funded under the European EUREKA scheme. Three partners share the work involved: The Acoustics Laboratory of The Technical University of Denmark; Bang and Olufsen of Denmark; and KEF Electronics of England. Its primary object is to quantify the influence of listening room acoustics on the timbre of reproduced sound. For simulation of the acoustics of a standard listening room, an electroacoustic setup has been built in an anechoic chamber. The setup is based on a computer model of the listening room, and it consists of a number of loudspeakers positioned on an imaginary sphere surrounding the position of the test subject. The setup has been designed for the highest degree of flexibility. This includes the possibility of simulation of directivity characteristics of normal domestic loudspeakers and absorption coefficients of the surfaces of the listening room. This paper is a presentation of the system, with special emphasis on the psychoacoustical background of the design. This will include a discussion of choice of experimental procedure, test stimuli, and test subjects as well as purpose built loudspeakers and the DSP system.

Soil samples collected from 26 organic and 550 conventional farms during autumn 1990 through the national Grid Net Survey (GNS) and a simultaneous supplementary survey on 8 organic farms have been analyzed in order to estimate the risk of nitrogen leaching. The average nitrate N (nitrogen) content in the soil (0–75 cm) was very similar in samples from organic farms (31kg/ha) and conventional farms using manure (29 kg/ha), but superior to that of conventional farms not using manure (22 kg/ha). Samples collected from fields on organic farms cultivated with grass with clover or alfalfa were very small (12 kg/ha) compared to samples from fields cultivated with cereals (57 kg/ha) and samples from bare fields following cereals (48 kg/ha). The average nitrate N content was higher in samples from clayey soil (40 kg/ha) than from sandy soils (15 kg/ha). The nitrate N content in samples from regions with a high percolation level during the autumn (August to December 1990) was lower than in samples from reg...

In this paper, we present an experiment based on a method called Temporal-Check-All-That-Apply (TCATA). The experiment was carried out to study the temporal perception of various attributes of sound quality when sounds move around a stationary listener. The first goal of the experiment was to understand if we could capture any changes in the perceived quality that reflected the spatial characteristics of the sounds reproduced in the lab using loudspeakers. The second goal was to evaluate if the method could record perceptual differences between stimuli with non-expert listeners. We concluded that TCATA is a suitable method to capture changes in the perception of various sound quality attributes over time. Still, we observed that dynamic physical characteristics are not necessarily represented as dynamic perceptual characteristics in all cases. The experimental variables programme, reproduction system, trajectory of a moving sound source, and loop showed a statistically significant effect on the results. Based on our findings, we propose recommendations for future investigations.