Acoustic Testing

Room Acoustic Modelling and Auralisation

Room Acoustic Modelling and Auralisation

Acoustic modelling is a useful and cost-effective tool for clients and acousticians to simulate the acoustic properties of a space before it is built. At ALFAdB we have access to various industry standard software (including EASE – Enhanced Acoustic Simulator for Engineers) that can be used across a wide range of applications to estimate room acoustic parameters and functions including :

The RT60 reverberation test measures the time required for a sound to decrease in intensity from its original maximum level by 60 decibels. RT60 is measured in seconds and often stated as a single value. The actual measurements span the frequency band from 50 Hz to 8000 Hz with 1/1 or 1/3rd octave resolution. Rooms have individual absorption capabilities for each frequency, so the RT60 values within each band will vary.

  1. ASTM E2235: Standard Test Method for Determination of Decay Rates for Use in Sound Insulation Test Methods
  2. ISO 3382-1: Specifies methods for the measurement of reverberation time and other room acoustical
    parameters in performance spaces
  3. ISO 3382-2: Specifies methods for the measurement of reverberation time in ordinary rooms.

Determining formant range of speech and frequencies in a way that emulates the type of sound pressure profiles actually present in rooms and turning data collected through impulse responses into something resembling the sound pressure in room with natural signals and then analyzing them.

Speech Transmission Index (STI) is a measure of speech transmission quality. The STI measures some physical characteristics of a transmission channel (a room, electro-acoustic equipment, telephone line, etc.), and expresses the ability of the channel to carry across the characteristics of a speech signal. STI is a wellestablished objective measurement predictor of how the characteristics of the transmission channel affect speech intelligibility. The speech intelligibility is measured by playing a known signal (the STIPA test signal) through the PA and measuring the quality of that signal as it reaches each of the measurement positions.

IEC 60268-16: IEC 60268-16 specifies objective methods for rating the transmission quality of speech with
respect to intelligibility. It provides a comprehensive manual for all types of users of the STI method in the
fields of audio, communications and acoustics.

The process of listening to any audio file as it would sound if played inside a simulated or measured space. a room’s measured or simulated impulse response, and an anechoic audio  is needed in order to produce an auralisation. A room’s impulse response is a short signal that fully represents the room’s acoustics, containing information such as the frequency response and the reverberation time.

The process of room acoustic modelling can assist the cost-effective design of a future space, from the correct amount and placement of reverberant treatment within a room, to understanding local effects for any proposed listener within the space. The success of any room acoustic model depends upon the user to generate a representative space including the acoustic characteristics of all surfaces within.


Room acoustic simulations allow the process of auralisation (i.e. hearing the effect of a room from acoustically replicating the space). It requires the process of convolution; mixing ‘clean’ audio recordings with impulse responses generated from the virtual space. The process is mainly applied to the acoustic planning of rooms used for music but can also be used for any large rooms for educational purposes. To give an indication of what the process of auralisation means, or to hear a virtual acoustic space, please try the dry and convoluted WAV files in the below player. This is an example taken from a large sports hall development that was intended to be used for music. The resulting Rt time was estimated to be compliant in accordance with BB93 Acoustic Design of Schools and the client was provided with sound files to demonstrate what the room would sound like before construction commenced.

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