In This Section
Journal of the AES
2014 January/February - Volume 62 Number 1/2
Although audio mixing has always been viewed as the artistic task of either a conductor balancing the musicians in a live performance or a mixing engineer combining multiple tracks in a sound studio, this research considers mixing as a mathematical optimization problem. Using an auditory model, the authors demonstrated how numerical optimization can be used to pose and solve a mix problem. There is interplay between artistic objectives, perceptual constraints, and engineering methods. Taking loudness as an example, it is shown that the nonlinearity in the perceptual model leads to complex behavior, which can be overcome by careful choice of optimization strategies and parameters.
A novel and computationally efficient method for evaluating the response of a perforated absorption panel with an arbitrary number of Helmholtz resonator elements is proposed. The method is based on a simplified, parametric filter-based model using 2nd-order parametric IIR digital filters that emulate both the linear filtering response of each resonator and the relative acoustic path delays and gains of responses. This allows for the evaluation of the time- and frequency-domain response of arbitrary-sized perforated panels in any specific receiver position under free-field and diffuse-field acoustic environments. Unlike existing analytical approaches, the proposed approach offers significant computational efficiency and allows flexible and fast practical evaluation of the effects of such panel absorbers.
By analyzing the frequency of low-level power line energy (Electrical Network Frequency, ENF) that has leaked into an audio recording, forensic researchers have been able to find the date and time when the recordings were made. This research implements an enhanced ENF extraction algorithm and evaluates the key parameters needed for optimizing its accuracy, such as sampling frequency, analysis window size, window increment, and the choice of harmonic components. For example, the use of odd harmonics, specifically the 5th, 7th, and 9th, for determining frequency is shown to create a better match to the reference database. Unlike current approaches to ENF analysis that use a combination of analog and digital technology, this approach is purely digital with the resulting benefits of reduced noise floor and flexible software algorithms.
The belief that the use of dynamic range compression in music mastering deteriorates sound quality needs to be formally tested. In this study normal hearing listeners were asked to evaluate popular music recordings in original versions and in remastered versions with higher levels of dynamic range compression. Surprisingly, the results failed to reveal any evidence of the effects of dynamic range compression on subjective preference or perceived depth cues. Perceptual data suggest that listeners are less sensitive than commonly believed to even high levels of compression. As measured in terms of differences in the peak-to-average ratio, compression has little perceptual effect other than increased loudness or clipping effects that only occur at high levels of compression. One explanation for the inconsistency between data and belief might result from the fact that compression is frequently accompanied by additional processing such as equalization and stereo enhancement.
By examining attributes of recorded music over many decades, larger patterns emerge as long-term trends. The authors suggested a set of signal features and examined the impact of limiters and compressors on a corpus of music tracks. From 1967 to 1984, mainstream music production tended toward high-fidelity and transparency, as a result of technological innovations. From 1984 to 2004, on the contrary, music tended toward low-fidelity and transient degradation. While the loudness war, which may have peaked in 2004, has indeed decreased “naturalness” in mainstream music and made it louder and transients less salient, the macrodynamics remain practically untouched. In other words, there are still pianissimi and fortissimi in recent mainstream music. The origin of the “ear fatigue” phenomenon, which is sometimes associated with modern music, does not lie with the absence of musical dynamics, but may relate to the ill-defined micro dynamics.
Standards and Information Documents
AES Standards Committee News
Audio-file transfer and exchange; measurement and equalization of sound systems in rooms; audio metadata
136th Convention Preview, Berlin
During the 135th Convention, held recently in New York, a series of events was devoted to explaining America’s National Recording Preservation Plan. This recently launched scheme acts as an example to the rest of the world of how massive national and governmental commitment to audio preservation can lead to a coordinated and systematic approach to a common problem.
137th Convention, Los Angeles, Call for Papers