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Journal of the Audio Engineering Society
The Journal of the Audio Engineering Society — the official publication of the AES — is the only peer-reviewed journal devoted exclusively to audio technology. Published 10 times each year, it is available to all AES members and subscribers.
The Journal contains state-of-the-art technical papers and engineering reports; feature articles covering timely topics; pre and post reports of AES conventions and other society activities; news from AES sections around the world; Standards and Education Committee work; membership news, patents, new products, and newsworthy developments in the field of audio.
2016 January/February - Volume 64 Number 1/2
Prior investigations have generally failed to confirm or deny the perceptual influence of high-frequency harmonics contained in musical sounds. Because harmonics that are beyond the frequency range of auditory detection influence the resulting waveform, they may alter the perception of a sound’s tonal character. This study found no evidence that capable listeners noticed an effect of high-frequency harmonics within a brief complex tone. With regard to the influence of high-frequency harmonic content on timbre perception, subjects were capable of performing the assigned task, the presentation technology was adequate for delivering reliable stimuli, the stimuli were appropriate for the interests of the study, and yet, there were no indications that the presence of high-frequency harmonics influenced listeners’ perception of the timbre of a complex waveform.
Adjusting the playing speed and signal pitch of an audio signal in a compressed representation, such as MP3, presents special challenges. The proposed approach modifies the input of the inverse modified discrete cosine transform in the process of MP3 decoding. The method provides a high-quality frequency shift from the mathematical model, which can extract the frequency, amplitude, and phase of the frequency components located at subband boundaries. Using the extracted information, frequency shifts were made and the performance of the proposed method was analyzed and compared with other methods by quantitative and subject tests. For a subjective analysis, the MOS test with five professional musicians was carried out. The subjects generally gave the result a score of 4. The proposed method has a computation complexity of approximately 43% of the synchronized overlap-add algorithm for MP3 music, which is known as a simple frequency-shift algorithm.
In the context of recorded sound there is great debate over which parameters influence the perception of quality. To gain insight into the dimensions of quality perception, subjective and objective evaluation of musical program material, extracted from commercial CDs, was undertaken. It was observed that perception of audio quality and liking of the music can be affected by separate factors. Familiarity with stimuli affected like ratings, while quality ratings were most associated with signal features related to perceived loudness and dynamic range compression. Additionally, the sonic attributes describing quality ratings indicate a diverse lexicon relating to timbre, space, defects, and other concepts. The results also suggest that, while the perceived quality of popular music may have decreased over recent years, like ratings were unaffected. Like ratings were strongly influenced by song familiarity, implying that aspects of preference and liking are distinct from the interpretation of quality and might not be the best descriptors for studies where technical quality is the percept being sought. Quality in music production is revealed as a perceptual construct distinct from hedonic, musical preference. Audio quality can be predicted from objective features in the signal, and can be adequately and consensually described using verbal attributes.
This paper shows that mechanical models of the materials used in loudspeaker suspensions may be more accurate by incorporating fractional derivatives in the model. In conventional differential equations, the differentiating order is a real integer, whereas for fractional derivatives the order is only constrained to be a real number with a fractional piece. The results of four loudspeakers with different types of suspension show that the proposed model with a single fractional element provides very low RMS error when compared to the measured data for all loudspeakers measured in standard atmosphere as well as in vacuum. Many materials used in loudspeaker suspensions exhibit significant frequency dependence of damping and compliance due to their various viscoelastic properties. Many physical processes, including the viscoelastic materials, exhibit fractional order behavior. In addition there exists a physical interpretation of the fractional derivatives, which makes them more compelling that a purely empirical model.
It is well known that the human perceptual system can adapt by changing its processing properties when exposed to feedback and context. The brain is not a fixed stimulus-response system. This report investigates auditory adaptation processes in spatial listening tasks for people with normal hearing ability. The auditory adaptation process to altered auditory cues of thirteen participants was monitored and compared to their normal hearing listening performance. Binaural room impulse responses were measured for each participant and for an artificial head. Listeners were trained to non-individual HRTF cues in an audiovisual training task. Ten out of thirteen listeners showed significant improvement in their ability to localize sound sources varying in elevation on the median plane after training. Two of these listeners performed better with trained artificial binaural room impulse responses than with their individual measured room impulse responses. Listening tests show that audiovisual training with artificial binaural room impulse responses decreases localization error significantly in the median plane.
On Some Biases Encountered in Modern Audio Quality Listening Tests (Part 2): Selected Graphical Examples and Discussion
Measuring audio quality is particularly difficult because the measurement methodology itself strongly biases the results. While a previous paper by the same author covered a broad range of biases, this report focuses only on five types of systemic error potentially affecting quantifying judgments: range equalization bias, stimulus spacing bias, contradiction bias, and biases due to nonlinear properties of the assessment scale. These biases are prevalent in audio and speech quality evaluations. Empirical data obtained by various researchers over the past fifteen years was used to illustrate biases in a graphical representation. The results conclusively show that assessment methods are inherently relative. These results also raise important questions about the utility of verbal descriptors. Researchers should avoid conclusions about quality by associating numerical scores with verbal descriptors at fixed positions along the scale.
Due to the size constraints of portable stereo listening devices, their small and closely spaced loudspeakers lead to a poor spatial sound image. An audio algorithms architecture is proposed to compensate for the weak sound image. The system is composed of a spatializer based on an improved version of the recursive ambiophonics crosstalk elimination algorithm, integrated with a combined quasi-anechoic equalization approach, and a virtual bass algorithm capable of enhancing the loudspeakers performance. The proposed solution has been successfully implemented on both Android and iOS operating systems. Listening tests show positive results. Although the spatializer is capable of enhancing the spatial impression, the main audio quality suffers, which therefore requires a compensating equalizer and virtual bass algorithm.
Standards and Information Documents
AES Standards Committee News
AES70 - Open Control Architecture for networks; AES67 audio over IP networks; XML implementation of audio decision lists; digital interface for microphones; microphone measurement and characterization
141st Convention, Los Angeles, Call for Papers
Analog recording media from yesteryear such as lacquer disks, 78 rpm records, and reel-to-reel tapes all suffer from different aging processes and fragilities that make it a challenge to deal with them safely and correctly, with the best chance of extracting the content for posterity with high sonic quality. Workshop presentations from the 139th Convention tackled the handling and restoration of difficult media.