Lion city soundscapes: Modified partitioning around medoids for a perceptually diverse dataset of Singaporean soundscapesa).

This study presents a dataset of audio-visual soundscape recordings at 62 different locations in Singapore, initially made as full-length recordings over spans of 9-38 min. For consistency and reduction in listener fatigue in future subjective studies, one-minute excerpts were cropped from the full-length recordings. An automated method using pre-trained models for Pleasantness and Eventfulness (according to ISO 12913) in a modified partitioning around medoids algorithm was employed to generate the set of excerpts by balancing the need to encompass the perceptual space with uniformity in distribution. A validation study on the method confirmed its adherence to the intended design.

Automation of binaural headphone audio calibration on an artificial head.

In studies with auralisation of audio stimuli over headphones, accurate presentation of headphone audio is critical for replicability and ecological validity. Audio stimuli levels are usually calibrated by placing studio quality headphones on an artificial head and torso simulator. Manual adjustment of audio tracks becomes laborious when the number of stimuli is large, especially for applications with large datasets. To increase reliability and productivity, we devised a stimulus-agnostic, automated calibration procedure for headphone audio via an artificial head and torso simulator, with a LabVIEW implementation available at doi:10.21979/N9/0KYIAU.•The procedure uses a National Instruments NI-9234 data acquisition module and works with any ITU­T P.58:2013 and ANSI/ASA S 3.36:2012 compliant artificial head measurement systems.•The procedure works by an adjustment to a generic guess, followed by a modified binary search, wherein the audio stimuli are calibrated to within a user-specified tolerance level.•Each stimulus in a validation run to calibrate 250 stimuli to 65.0 ± 0.5 dB was played back an average of 2.22 ± 0.92 times before successful calibration, thus demonstrating the robustness and efficiency of our proposed method.

Active control of broadband sound through the open aperture of a full-sized domestic window.

Shutting the window is usually the last resort in mitigating environmental noise, at the expense of natural ventilation. We describe an active sound control system fitted onto the opening of the domestic window that attenuates the incident sound, achieving a global reduction in the room interior while maintaining natural ventilation. The incident sound is actively attenuated by an array of control modules (a small loudspeaker) distributed optimally across the aperture. A single reference microphone provides advance information for the controller to compute the anti-noise signal input to the loudspeakers in real-time. A numerical analysis revealed that the maximum active attenuation potential outperforms the perfect acoustic insulation provided by a fully shut single-glazed window in ideal conditions. To determine the real-world performance of such an active control system, an experimental system is realized in the aperture of a full-sized window installed on a mockup room. Up to 10-dB reduction in energy-averaged sound pressure level was achieved by the active control system in the presence of a recorded real-world broadband noise. However, attenuation in the low-frequency range and its maximum power output is limited by the size of the loudspeakers.

Feedforward multichannel virtual-sensing active control of noise through an aperture: Analysis on causality and sensor-actuator constraints.

The multichannel implementation of the auxiliary-filter-based virtual-sensing (AF-VS) technique for active noise control applications is revisited and realized in the paper. Frequency-domain analysis based on random primary noise proves that the multichannel virtual-sensing active noise control (MVANC) technique can achieve optimal control at the desired virtual locations even if the signals at the physical and virtual microphones are not causally related. Further analysis on a number of sensor-actuator configurations shows that the MVANC technique achieves optimal control at the desired locations as long as the number of secondary sources does not exceed that of the physical error microphones. Furthermore, the simulations with measured transfer functions and real-time experiments conducted on a four-channel system validate the frequency domain analyses.

Effects of adding natural sounds to urban noises on the perceived loudness of noise and soundscape quality.

Introducing pleasant natural sounds to mask urban noises is an important soundscape design strategy to improve acoustic comfort. This study investigates the effects of signal-to-noise ratio (SNR) between natural sounds (signal) and the target noises (noise) and their temporal characteristics on the perceived loudness of noise (PLN) and overall soundscape quality (OSQ) through a laboratory experiment. Two types of urban noise sources (hydraulic breaker and traffic noises) were set to A-weighted equivalent sound pressure levels (SPL) of 55, 65, and 75 dB and then augmented with two types of natural sounds (birdsong and stream), across a range of SNRs. Each acoustic stimulus was a combination of noise and natural sound at SNRs from -6 to 6 dB. Averaged across all cases, the subjective assessment of PLN showed that augmenting urban noise separately with the two natural sounds reduced the PLN by 17.9%, with no significant differences found between the birdsong and stream sounds. Adding natural sounds increased the OSQ by on average 18.3% across the cases, but their effects gradually decreased as the noise level increased. The OSQ of the birdsong and stream sounds were similar for traffic noise, whereas the stream sound was rated higher than the birdsong for the breaker noise. The results suggest that increasing the dissimilarity in temporal structure between the target noise and natural sounds could enhance the soundscape quality. Appropriate SNRs were explored considering both PLN and OSQ. The results showed that the SNR of -6 dB was desirable when the A-weighted SPL of the noise rose to 75 dB.