Sunday, May 21, 09:30 — 12:30
EB02-01 AKtools—An Open Software Toolbox for Signal Acquisition, Processing, and Inspection in Acoustics
Fabian Brinkmann (Presenting Author), Stefan Weinzierl (Author)
The acquisition, processing, and inspection of audio data plays a central role in the everyday practice of acousticians. However, these steps are commonly distributed among different and often closed software packages making it difficult to document this work. AKtools includes Matlab methods for audio playback and recording, as well as a versatile plotting tool for inspection of single/multichannel data acquired on spherical, and arbitrary spatial sampling grids. Functional blocks cover test signal generation (e.g., pulses, noise, and sweeps), spectral deconvolution, transfer function inversion using frequency dependent regularization, spherical harmonics transform and interpolation among others. Well documented demo scripts show the exemplary use of the main parts, with more detailed information in the description of each method. To foster reproducible research, AKtools is available under the open software European Union Public Licence (EUPL) allowing everyone to use, change, and redistribute it for any purpose: www.ak.tu-berlin.de/aktools.
Engineering Brief 309
EB02-02 Disagreement between STI and STIPA Measurements Due to High Level, Discrete Reflections
Ross Hammond (Presenting Author), Adam Hill (Author), Peter Mapp (Author)
Objective measures of intelligibility, speech transmission index (STI), and speech transmission index for public address systems (STIPA) often form the basis for sound system verification. The reported work challenges the accuracy of both measures when encountering high level, discrete reflections. Tests were carried out in an anechoic environment with artificial reflections added between 0 and 500 ms. Discrepancies were found to occur above 80 ms due to synchronization between modulation frequencies and reflection arrival times. Differences between STI and STIPA of up to 0.1 were found to occur for the same delay condition. Results suggest STIPA should be avoided in acoustic environments where high level, discrete reflections occur after 80 ms and STI should only be used alongside other verification methods.
Engineering Brief 310
EB02-03 Soundscape Recording: Review of Approaches
Katarzyna Sochaczewska (Presenting Author), Dorota Czopek (Author), Pawel Malecki (Author), Jerzy Wiciak (Author)
In the soundscape analysis the collected data is crucial for possible relationships between the results of measurements of acoustic, psychoacoustic research results, and characteristics of the respondents. Such analysis shall verify that the physical characteristics of sound affect the subjective assessment. The article shows a review of commonly used approaches in soundscape recording both for analysis and archive purposes. Discussion on recording from one or several spots in the middle of the sound sources versus moving with the microphone towards or inside the acoustic environment is provided. Also, special attention is paid on traditional microphone techniques in sound engineering, binaural recordings, and sound field synthesis with spherical harmonics.
Engineering Brief 311
EB02-04 Ambience Recording for 3D Audio
Marco Hanelt (Presenting Author), Andreas Ehret (Author)
3D audio is emerging as a production format to enable immersive consumer audio experiences, including the sensation of height. This eBrief focuses on the use of 3D microphone arrays for recording 3D ambiences. Multiple microphone arrays were evaluated, both in theory as well as in practice. The arrays were assessed for their perceptual performance such as spatial envelopment, location accuracy, and timbre. Furthermore, the practical usability of these recordings in a real world movie project and the handling in a common post-production environment have been tested. With the information gathered, a Best Practice guide for different use cases has been developed.
Engineering Brief 312
EB02-05 Do Microphone Angles Result in Audible Differences When Recording a Guitar Amplifier?
Ellen Culloo (Presenting Author), Malachy Ronan (Author)
Objective measurements using a sinusoidal sweep show that microphone angle has little effect on the frequency response of a guitar amplifier recording . However, anecdotal evidence suggests that alterations to the microphone angle hold merit when recording ecologically valid sound sources. An ABX listening experiment was conducted with 20 participants to investigate whether microphone angles of 0, 30, and 60 degrees were audibly different to this cohort. Both dynamic and ribbon microphones were used and the loudness normalized guitar recordings were presented in solo and within a music mix. The experimental results suggest that microphone angles did not generate any perceivable changes to this cohort on this program material.
Engineering Brief 313
EB02-06 The Mixing Glove and Leap Motion Controller: Exploratory Research and Development of Gesture Controllers for Audio Mixing
Jack Kelly (Presenting Author), Diego Quiroz (Author)
Digital musical instruments (DMIs) have been evolving over the past several decades, and much research has been done on the subject of capturing the gestures of performers in an effort to re-map them to digital instruments. The practice of audio mixing is no different from a musical performance in this respect. The gestures used by engineers are expressive and have complex metaphorical significance. In this paper two approaches to gesture-based mixing tools for audio engineers, the Mixing Glove and the Leap Motion Controller are explored. Both systems are designed to control volume, panning, solo/mute, and reverb, using hand gestures alone.
Engineering Brief 314
EB02-07 Discussion on Subjective Characteristics of High Resolution Audio
Mitsunori Mizumachi (Presenting Author), Katsuyuki Niyada (Author), Ryuta Yamamoto (Author)
High resolution audio gains in popularity on both audio production and consumer markets. It is necessary to characterize the advantage of high resolution audio over legacy audio formats. The authors have already reported perceptual discrimination rates for high resolution audio, that is, 192 kHz/24 bits PCM format, against a 48 kHz/16 bits format and its compressed versions under a listening room and in-car environments, respectively. In this paper we also focus on perceptual discrimination concerning bit depth in between 24 and 16 bits. Participants were asked to judge either the same or not for each paired stimulus of 48 kHz/24 bits and 48 kHz/16 bits formats. The discrimination rates depend on the reproduction environments, although those subjects could discriminate the difference in between 192 kHz/24 bits and 48 kHz/16 bits formats. It is supposed that high resolution audio benefits more from the wide frequency range than from the bit depth.
Engineering Brief 315
EB02-08 Accurate Extraction of Dominant Reflections from Measured Sound Intensity Responses in a Room
Masataka Nakahra (Presenting Author), Yasuhiko Nagatomo (Author), Akira Omoto (Author)
The intensity responses in three orthogonal directions, which are calculated from measured impulse responses, include information of dominant reflections in 4-pi space. This information is important for restoration of a sound field, e.g., a spatial reverberator. A method of extracting significant reflections from instantaneous intensities or their envelopes is, therefore, the key application element. To improve the accuracy of detecting reflections, the authors have introduced a new strategy, named “speed detection,” which calculates the moving speed of instantaneous intensities at every sampled time. If the speed is lower than an assumed threshold, these intensities indicate reflections. On the contrary, faster speeds indicate the residual transient components of intensities. This “speed detection” is verified with the measured data of several experiments.
Engineering Brief 316
EB02-09 Investigation of Interchangeability of Audio Objects' Spatial Sound Direction between 3D Audio Rendering Systems and Rooms by VSV (Virtual Source Visualizer)
Takashi Mikami (Presenting Author), Masataka Nakahara (Author), Akira Omoto (Author)
Recently, some kinds of 3D sound rendering systems (such as Dolby Atmos, DTS:X, 22.2ch. etc.) are proposed and commercialized in audio industries. Similarity / difference in 3D sound localizations were examined by using sound intensity. Sound intensities are measured on different rendering systems in the same room, and also on the same rendering systems in different rooms. Subjective study to evaluate 3D sound rendering systems requires much time and labor. Evaluation by sound intensities, measured physically, is very useful. The session discusses interchangeability / difference of sound direction between rendering systems and between rooms obtained by analyzing the visual images and numerical data of sound localization.
Engineering Brief 317
EB02-10 Loudness Management in the Blu-ray Disc Ecosystem in the Context of Today’s Playback Environments
Andreas Ehret (Presenting Author), Sripal Mehta (Author), Mike Ward (Author)
Loudness management within the Blu-ray Disc ecosystem has historically been less of a priority than in other media playback ecosystems. Instead, the industry has focused on delivering the highest fidelity and full dynamic range audio. As a result, the measured loudness of the content on Blu-ray Disc is generally not accurately indicated in the audio bitstreams carried on Blu-ray discs. However, as more use-cases emerge to connect Blu-ray Disc players to playback environments with limited dynamic range reproduction capabilities (such as TVs or Sound bars), loudness management is becoming more important to ensure optimal playback for these new device types. This brief explains the value of loudness management in the Blu-ray Disc ecosystem to address new playback environments and gives example workflows for correctly setting loudness values in audio bitstreams delivered on Blu-ray Disc.
Engineering Brief 318