Speech Intelligibility in Acoustic Consultancy

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Speech Intelligibility in Acoustic Consultancy
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What is Consultancy?

• Borrow your watch to tell you the time
• and charge you for it!
• Take a large body of understanding,
• multiplied by a significant effort of analysis,
  
• present it with all the intellectual demands
  stripped out
• but with all the wisdom intact!
• and charge you for it!

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Acoustic Consultancy

• Acoustics in the built environment
• Aural environment and the well-being of humans
• Practical aesthetics
• Invisible aesthetics
• Functions requiring spoken communications
• Opportunities to deliver value through
  identifiable (quantifiable) needs

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Acoustic Consultancy

• disaster as the mother of necessity!
• Kings Cross Fennel Report
• Hillsborough Stadium Taylor Report
• Legislative requirements for speech
  intelligibility
• Stakeholders in speech intelligibility
• Developers, owners, operators
• Railway stations, airports etc
• Aircraft
• Sports stadia
• Shopping centres
• Public spaces

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Amplified Speech InformationSignal Chain
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Speech Transmission Index

• STI
• RASTI Rapid Assessment method
• MLS/Sweep methods STI
• STI-PA
• National and International Standards for Voice
  Alarm propose or require RaSTI gt 0.5
• RaSTI is a measurement method. STI is the
  metric.
• If 0.5 not practicable, 0.45 may be arguable.

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Design Requirements Architectural Integration
Speech Intelligibility
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Design Requirements Architectural Integration
Speech Intelligibility Electroacoustic
evaluation
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Sources of Noise
The Model
Words words words ...
Internal Noise - activities within the building
HVAC
Equipment fans
ExternalNoise - activities outside the building
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Noise Level Profile Small Station
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FUNDAMENTALS 2 - Noise
Words words words ...
Noise
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Signal Levels

• understand noise levels/conditions
• 5dB, 10dB, 15dB above?
• 60dBA minimum
• 75-80dBA getting loud.
• 80-85dBA not normally much net benefit beyond
  this
• 85-90dBA extreme conditions

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FUNDAMENTALS 3 - Reverberance
Words words words ...
Reverb
Reverb Noise
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Acoustic response
Direct sound
Early reflections - integrated
Late reflections - characterises the space
gt Reverberance
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Acoustic response
Earlyreflections
Direct
Late reflections developing into reverberance
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Acoustic Response - Reverberation
Acoustic Response - Reverberation
Trying to understand the spoken word in the
presence of reverberation is like trying to read
text where the ink has been smeared from left to
right. Each sound runs into the next.
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Achieving intelligibilityin acoustic terms
Arup Acoustics
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Achieving intelligibilityin building terms 1
Arup Acoustics
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Achieving intelligibilityin design role terms 3
acousticresponse
loudspeakerlayouts
specialistsystem design
architecture
building services
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Speech Transmission Index

• Promotes control of acoustic conditions AND
  loudspeaker solution
• Single figure widely adopted
• Accounts for (generic) noise and late energy
  effects
• Does not account for noise character
• open plan classroom
• Multiple message broadcasts
• Does not account for spatial separation
• Overhead loudspeakers versus lateral noise
  sources
• Directionally weighted late energy field
  underground platform

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Speech Intelligibility
Reflection Timings and Relative Level to
Source Strong Early Reflections Improve
Intelligibility (0-50ms) Strong Late Reflections
Reduce Intelligibility (gt50ms)
Amplitude
Time
50 ms
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SoundLab Principle

• 3D room response at listener position
  predicted using computer models or measurements
  of existing rooms

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Process of Creating an Auralisation
Computer Model or Real Space
Emitted impulse
Measured Impulse
Amplitude
Amplitude
Time
Time
Anechoic Speech
Sound in the SoundLab
Measured Impulse
Amplitude
Time
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SoundLab Principle

• 3D room response at listener position
  recreated using Soundlab

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Inside Arup SoundLab
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Counsel
Source
Intelligibility
Reverb Time
0 0.1 0.2 0.3 0.4 0.5
0.6 0.7 0.8 0.9 1.0 gt1.0
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What is Consultancy? with Auralisation

• Borrow your watch to SHOW you the time
• and ask you tell it yourself!
• Take a large body of understanding,
• multiplied by a significant effort of analysis,
  
• present it with all the intellectual demands
  stripped out
• but with all the wisdom intact!
• and ask you to make your own mind up!
• Evaluate real options
• Present FEASIBLE renderings to make the decisions
  comprehendible