Impact
of Armstrong i-ceilings Sound Field to
provide a better learning environment:
It is accepted that good speech intelligibility is a fundamental
requirement when designing teaching environments. Whilst BB93
focuses on reverberation time, consideration is given to the
other basic elements required to provide speech intelligibility.
Most students will be able to hear the teacher but not all
can actually understand what is being said. The ability to
communicate effectively within a classroom, or any space,
depends on a few basic elements:
• Appropriate reverberation
time (RT)
• Signal to Noise Ratio (SN)
• Appropriate sound pressure level (SPL)
Combined at the optimum levels these elements will produce
a classroom that evolves into a communication tool rather
than a facility built to simply ‘meet-and-teach’.
-
Speech Intelligibility (STI)
The speech transmission index is an objective measure defined
in BS EN 60268-16:1998, accountng for all variables in room
acoustics eg. room design, volume and surface materials. The
index provides a guide to what RT is acceptable to create
an effective communication space.
- Reverberation time (RT)
The RT index is used to determine how quickly sound decays
in a room. The physical volume and surface materials used
in the room dictate the RT characteristics.
Measured
in time, high values represent more 'lively' resonating spaces
- or increased 'echo'.
Lower values indicated more dry spaces. Classroom environments
are measured using the average value of RT from three specific
octave bands centered at frequencies of 500Hz, 1000Hz &
2000Hz.
- Loudness (SPL)
SPL is an indication of the loudness of a source (noise).
eg, Normal speaking voice is about 60 dB(A)
120dB is the 'threshold of feeling'
130dB is artillery fire at 1 metre
140dB (threshold of pain) is a jet aircraft at 5 metres
- Signal to Noise (SN): Dynamic
range
Signal to noise ratio measures the difference in loudness
between ambient noise (background sounds like air conditioning,
whirring of computer fans or even external noise such as road
or air traffic) and the signal (the speaker or person speaking).
If the difference in loudness is too small, then background
noise will disrupt the intelligibility of the speaker.
Graphs
demonstrate the value of considering both passive and active
acoustical treatments in the design of classrooms. |
