reported
by: Dr. Roland K C Tan
Secretary (Term
1995/96)
On July 11, 1995, Singapore
members, together with a good mix of more than 30 invited guests from
the sound industries including those from the neighbouring countries, met at
the posh Pinetree Country Club. After a warm welcoming speech
delivered by Mr. Arthur Ngiam, one of the most senior AES
members in Singapore and also the main sponsor for the half-day morning
event, the audience was treated to an enlightening lecture on an overview of
"Sound Enhancement Techniques" by Dr. Roland Tan,
secretary to the local section.
Dr. Tan first began with a
lecture on the psychology of hearing. He introduced the Fletcher-Munson
curve plots, then highlighted the audible frequency range of normal hearing
and explained how the ear's sensitivity varies at different frequency
region. He also discussed how sound can be detected over a wide dynamic
range of more than 100dB which justified the need for a higher resolution
digital audio format of more than 20-bit. The digitisation of audio signal
using PCM introduces quantization distortion.
Dr. Tan carefully explained
with illustrations, on how these undesirable distortions have been
effectively overcome using dithering and noise shaping techniques. An
efficient data compression technique using perceptual coding must be applied
to substantially reduce the high data rate associated with the current as
well as future digital audio format. Dr. Tan stressed that perceptual
coders, which consider psychoacoustic noise masking effects such as those
found in MPEG standards, were necessary. He went on to describe about the
MPEG I and II audio coders. This was followed by an interesting sound
enhancement demonstration using the Philips IS 5022 sound enhancers.
The second lecture on "System
and Retrieval of Compressed Digital Audio Information using Solid State
Memory Technology" was conducted by Mr. Ger Janssen,
marketing manager of Philips in Eindhoven. He also discussed the MPEG
standard for audio compression and products based on these technologies.
With the introduction of the solid state audio playback system, it makes
repeated announcements such as those found in airports, railway stations,
stores, exhibitions, theatres, etc ideal with no degradation through
repeated use at CD quality audio! Unlike the analogue tape system with
moving parts, it is generally more rugged and is immune to dust, humidity
and temperature shifts. Such adverse environmental conditions is profound in
tropical climate and is a reality in this region.
A lively question-and-answer
session followed, extending the time till 1.30pm which was way past lunch
hour! There was no doubt about the growing interests in digital audio
processing technologies which could be felt from the audience in the ASEAN
region. |
