Auralisation

Convolution reverb is the process used for reverberating a signal by an impulse response of an actual space. The product of this operation is a third signal, containing reverberation of the space where the impulse response is captured. This project is based on creating a convolution reverb plugin on MaxMSP and evaluating the perceptual quality of convolution reverb.
The real-time fast convolution reverb plugin was implemented using multiple frequency delay line non-uniform partitioned convolution method on MaxMSP. An experimental design methodology was introduced in order to evaluate the perceptual quality of convolution reverb. In order to realise, anechoic drum kit music samples were recorded and re-recorded in a chamber to form the control signal. Also, using same equipment and setup, an impulse response was captured in the same chamber to form the test sample. These samples were then used for subjective analysis in a pair-wise categorical preference type listening test. The samples were also analysed in their spectrogram views in order to analyse the quality objectively.
Listening tests were designed so that realism, quality and personal preference categories were present. Null hypothesis was proved, where the realism difference of the two samples resulted in 52% of the participants preferring chamber reverb (control signal). However personal preference category resulted in 61%of the subjects preferring the chamber reverb. This was justified by objective analysis, where the convolution reverb shown to be having a faster decay rate for high frequency bands, thus sounding unnatural.

Archeologists find remains of circular earthworks with marks of timber palisades or stone circles in many parts of Europe. This article gives an overview of acoustic measurements made at two reconstructed timber circles in Central Germany. These measurements, combined with personal experiences, have been performed to explain the aural experiences at these sites. For determining the acoustic criteria for open-air monuments, textbook theories and practices were adapted. Most of the experiences in the circles can be explained by acoustic theory (such as: first reflection) but not all, since some aural interpretations are cultural. This made it difficult to determine the former aural usage of the prehistoric monuments. Since aural experiences are extremely important in present-day society, for pleasure and for religious reasons, just as they would likely have been for prehistoric people. The authors recommend utilising the acoustic properties of timber and stone monuments for future performances, to stimulate a better understanding of their acoustic and aural impact in the past and present.

Existing studies show that there are strange acoustical effects at the prehistoric sites. The resonances found at European prehistoric sites are generally in the frequency range of 90 – 120 Hz. The effects of listening to tones on regional brain activity at this frequency range have been studied before. This study is an investigation into the perceptibility of the resonances in the aforementioned frequency range, using a technique called auralisation. Bass response of the auralisations of a prehistoric hypogeum (Hal Saflieni Hypogeum, Malta) and a modern cathedral (Saint-Etienne, France) is analysed using spectral audio analysis methods. An ABX listening test was designed and carried out to test the hypothesis. The quantitative results of the subjective listening tests showed that subjects could differentiate between the two audio files. Combined with the findings from spectral analysis of the audio files, the study is concluded that the resonances found in the auralisation of Hal Saflieni Hypogeum are perceptible, thus, perceptual studies about the effects and possible use of the prehistoric sites need to be urged in order to discover the forgotten cultures and knowledge. Recommendations for further work are stated.