In This Section
Journal of the AES
2011 July/August - Volume 59 Number 7/8
In many loudspeaker systems high levels of air compression pressure result in turbulent noise if there are any air leaks. Traditional measurement techniques have difficulty identifying this particular defect because the resulting noise is wideband with low-power density, which is easily masked by environmental noise. A new technique designed to detect this kind of defect is based on asynchronous demodulation and envelope averaging. By accumulating the total energy of air leak noise, detection sensitivity increased by 20 dB for a 1-second measurement interval. This approach exploits the spectral information between the higher-order harmonics.
A Subjective Evaluation of the Minimum Channel Separation for Reproducing Binaural Signals over Loudspeakers
While there are a variety of methods and tradeoffs for creating the necessary crosstalk cancellation when reproducing a binaural signal through loudspeakers in a real environment, there are no studies that reveal the minimum required crosstalk. In the current study the authors simulated varying degrees of crosstalk in order to determine the required threshold. For most audio signals crosstalk should be below –15 dB, and for broadband signals the crosstalk should be below –20 dB. Off-center locations require even lower crosstalk.
A validated computational model of perceived spaciousness in sound recordings serves to represent the subjective experience of listeners. Three dimensions of spaciousness form the basis of the model: width of source ensemble, extent of reverberation, and extent of immersion. The model is trained and tested to learn the audio parameters that contribute to these three dimensions. The resulting model predicted spaciousness 32% above that of a baseline predictor. The model can be used to show an audio engineer the value of the three dimensions in real time.
Three-dimensional optical reconstruction using two-dimensional optical flow measured on the rotating groove surfaces of gramophone recordings will enhance our ability to preserve this valuable audio legacy without depending on mechanical contact playback. A modified microscope overcame the limitation of a shallow depth of field by using a thin glass plate to obtain an image at a second focal length. Sound is decoded from the orientation of the groove surface. The algorithm has been tested and validated using both damaged and undamaged records. Informal listening tests confirmed a subjective reduction of pops and other degradations.
Standards and Information Documents
AES Standards Committee News
Audio-file transfer and exchange; digital audio over ATM networks; transmission of ATM cells over Ethernet physical layer; unique identifiers in AES3 transport stream; sample-accurate timing in AES47; multichannel audio in AES3; audio applications of networks
130th Convention Report, London
131st Convention Preview, New York
131st Convention Exhibit Previews
44th Conference Preview, San Diego
Led by David Bialik, broadcast technology experts met at the 129th Convention in San Francisco to explore the expanding world of Internet streaming. All sorts of issues have been thrown up by this new technology and it is revolutionizing broadcasting. The speed at which it has happened is remarkable and the sound quality that can be delivered has become impressive. Whereas streamed sound quality started out being poor, it has now reached the point where is can exceed that of FM in some cases. Streamed services now also reach almost as many listeners as conventional broadcast radio, so it cannot be dismissed as a passing fad.
43rd Conference Preliminary Program, Pohang