Week 3 - Annotated Essay - 3-D acoustic space and its simulation using Ambisonics.

Week 3 - Annotated Essay - 3D Acousitc Space PDF (Click - Login)

Read the following sections
-Physiological considerations
-Perceptual issues
-The Effect of the Acoustics of the Performance Space

The reading ‘3-D acoustic space and its simulation using Ambisonics’ by David Malham, describes how acoustic space can be interpreted differently due to direction perception mechanisms, some of which were described include Interaural Time Delay, Interaural Time Difference, and head movements of a person. Orientation of sounds sources in acoustic space can be analysed also from other perception mechanisms to do with distance. Some of which are determined by frequency, reverberation, loudness and early reflections.

David Malham is explaining how sound in space can be interpreted differently due to perception mechanisms. Human sound sense is incredible to the point where it provide insights of our spatial environment, which our sight perception sometimes wouldn’t recognise. Malham mentions about perceptual issues, such that “it is widely, but perhaps wrongly, accepted that when we talk about our perception of what we call reality, it is the visual sense is pre-eminent.” He goes on to describe how without the “correct soundscape they lose much of their depth, becoming just the picture.” A solution to the right perceptual spatial environment is through the “reality equivalence” of the sound and the visual. In terms of the effect of the acoustics of a performance space Malham mentioned that there are two concerns about ambsisonic diffusion.

Understanding how perception mechanisms help us observe our spatial environment is helpful when applying to solve an architectural problem. For example striving for reality equivalence in an architectural performance space is important. It is not only what you see with your eyes that determine reality but what you are able to hear provides this equivalence. Also in the design of a performance space, the designer needs to take great consideration when dealing with the local and effects and the overall acoustics. For example positioning speakers from any reflected surfaces can prevent diffusion of sound, and trying to get loudspeakers to reproduce sounds that appear closer. These are the consideration when designing a performance space that an architect must consider.

Bibliography:
- David Malham, 3-D acoustic space and its simulation using Ambisonics.

Week 2 - Annotated Essay - Reverberation

Week 2 - Annotated Essay - Reverberation PDF (Click - Login)

The readings about reverberation from the book ‘Sonic Experience – A guide to everyday sounds’, describes the fundamentals of reverberation, and the effect it has in difference spatial surrounds. Reverberation in Sonic Experience is described by the time takes for the sound to decrease to 60DB (decibels – measure the intensity of sound), which is equivalent to the intensity of sound from a typical conversation. The measurement of reverberation time - RT60 is proportional with the volume of the room. When being placed in a room, you are able to determine “acoustic specificities” by analysing the RT60 curve.

This analysis can inform my own architectural practice in a way of understanding the built space, or unbuilt space. Architecturally speaking if I were to create a room for performance purposes such as a concert hall, I would need to think about the reverberant sound. In a concert hall the reverberant sound dies away over a period of time with the sound energy being absorbed by certain material interactions within that space. If I wanted to create a hall that would resonate throughout for a long period of time for an Opera I would need a more reflective room that would take longer for the sounds to fade away. This can be influenced by materials in the room which are good reflectors or are good at absorbing the sounds. In this example, good reflectors may be appropriate to get a longer reverberated time. Of course the reverberation time for any room should be proportional to intended use. So the reverberation time is the time it drops to 60 dB below original level expressed as RT60.

To determine what a good architectural reverberation time for a hall is, it is good to observe other examples of proficient halls, for example the New York, Carnegie Hall reverberation time is 1.7 seconds.

Bibliography:

• Reverberation Time, hyperphysics, Viewed 27 Junly 2012,
• Augoyard, Jean-Francois & Torgue, Henry, 2006, Sonic Experience – A Guide To Everydays Sounds, McGill-Queen’s University Press, London