Planning Room Acoustics Using A Hybrid Approach

By Author: Kevin Richard
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This post discuses a hybrid approach for planning the acoustics of the room. Here at O’Neill Engineered Systems, multiple techniques are incorporated into a single model, thereby enhancing precision and maintaining viability. Let us learn how this can be done.
Room acoustics review
Here, we will discuss how the two techniques can be blended to get a broadband impulse response for a room.
Room impulse response
The microphone will get direct sound from the first wavefront and also a superposition of all the reflected signals from the waves bouncing and travelling off the ceiling, floor, walls and other objects in a room. Sound is generally absorbed by various materials, like those of any ceiling tile, furniture and carpet for instance, implying the sound will ultimately die down completely until it is serene again. The time signal versus the acoustic pressure recorded by the microphone is known as the room impulse response as the measured location. This is quite vital descriptor of room acoustic, as it can tell much about how the room will sound.
Room ...
... modelling
While modelling the room acoustics, a simulation engineer should pay attention to both the geometric and acoustic scales to determine the precision and viability of a modelling approach. In the Acoustics Module, the low-frequency, modal behaviour of a room can be modelled with the finite element technique using the Frequency Domain interface and pressure acoustics. Nonetheless this approach becomes costly at high frequencies die to mesh needs. The high-frequency, echo behaviour of rooms can be modelled with the ray-tracing technique. While this technique is generally computationally effective, ray tracing is not a wave based technique and won’t capture modal behaviour. To precisely model the impulse response of a room, both models can be run in their respective frequency ranges and blended to get the response over the whole frequency range.
Pressure acoustics
Ideally, we may like to model the room using wave based techniques throughout the entire frequency range, but this might not be viable at high frequencies due to mesh needs. As we understand the contribution of individual modes dominates the room response below the Schroeder frequency, we will select to resolve the pressure acoustics using a maximum frequency that is slightly higher than the Schroeder frequency.
Combination technique
The results from the ray acoustics and pressure acoustics models can be blended to create a broadband impulse response signal. This may be done by taking a low-pass filtered pressure acoustics response and adding it to the high-pass filtered ray acoustics response. This technique emphasizes the linearity property.
The filter type used and the designation of the place to filter the signals is not set by any engineering standard. The applied digital signal processing method can be chosen based on industry oriented trend or engineering judgement. This model displays the combination concept using easy step filters that filter the signal.