3,561 research outputs found
2D to 3D ambience upmixing based on perceptual band allocation
3D multichannel audio systems employ additional elevated loudspeakers in order to provide listeners with a vertical dimension to their auditory experience. Listening tests were conducted to evaluate the feasibility of a novel vertical upmixing technique called “perceptual band allocation (PBA),” which is based on a psychoacoustic principle of vertical sound localization, the “pitch height” effect. The practical feasibility of the method was investigated using 4-channel ambience signals recorded in a reverberant concert hall using the Hamasaki-Square microphone technique. Results showed that the PBA-upmixed 3D stimuli were significantly stronger than or similar to 9-channel 3D stimuli in 3D listener-envelopment (LEV), depending on the sound source and the crossover frequency of PBA. They also significantly produced greater 3D LEV than the 7-channel 3D stimuli. For the preference tests, the PBA stimuli were significantly preferred over the original 9-channel stimuli
Effect of Vertical Microphone Layer Spacing for a 3D Microphone Array
Subjective listening tests were conducted to investigate how the spacing between main (lower) and height (upper) microphone layers in a 3D main microphone array affects perceived spatial impression and overall preference. Four different layer spacings of 0m, 0.5m, 1m, and 1.5m were compared for the sound sources of trumpet, acoustic guitar, percussion quartet, and string quartet using a nine-channel loudspeaker setup. It was generally found that there was no significant difference between any of the spaced layer configurations, whereas the 0m layer had slightly higher ratings than the more spaced layers in both spatial impression and preference. Acoustical properties of the original microphone channel signals as well as those of the reproduced signals, which were binaurally recorded, were analyzed in order to find possible physical causes for the perceived results. It is suggested that the perceived results were mainly associated with vertical interchannel crosstalk in the signals of each height layer and the magnitude and pattern of spectral change at the listener’s ear caused by each layer
The reproduction of the response of an aircraft panel to turbulent boundary layer excitation in laboratory conditions
One important topic in the aeronautic and aerospace industries is the reproduction of random pressure field, with prescribed spatial correlation characteristics, in laboratory conditions. In particular, the random-wall pressure fluctuations induced by a Turbulent Boundary Layer (TBL) excitation are a major concern for cabin noise problem, as this
excitation has been identified as the dominant contribution in cruise conditions. As in-flight measurements require
costly and time-consuming measurement campaigns, the laboratory reproduction has attracted considerable attention
in recent years. Some work has already been carried out for the laboratory simulation of the excitation pressure field
for several random fields. It has been found that TBL reproduction is very demanding in terms of number of loudspeakers per correlation length, and it should require a dense and non-uniform arrangement of acoustic sources due to
the different spanwise and streamwise correlation lengths involved. The present study addresses the problem of directly simulating the vibroacoustic response of an aircraft skin panel using a near-field array of suitably driven loudspeakers. It is compared with the use of an array of shakers and piezoelectric actuators. It is shown how the
wavenumber filtering capabilities of the panel reduces the number of sources required, thus dramatically enlarging
the frequency range over which the TBL vibro-acoustic response is reproduced with accuracy. Direct reconstruction
of the TBL-induced panel response is found to be feasible over the hydrodynamic coincidence frequency range using
a limited number of actuators driven by optimal signals. It is shown that piezoelectric actuators, which have more
practical implementation than shakers, provide a more effective reproduction of the TBL response than near-field
loudspeakers
Investigation on the Phantom Image Elevation Effect
Listening tests have been carried out in order to evaluate the phantom image elevation effect depending on horizontal stereophonic base angle. Seven ecologically valid sound sources as well as four noise sources were tested. Subjects judged the perceived image positions of phantom centre image created with seven loudspeaker base angles. Results generally showed that perceived images were elevated from front to above as the loudspeaker base angle increased up to around 180°. This tendency depended on the spectral characteristics of sound source. The perceived results are explained from both physical and cognitive points of view
- …