Implementing digital engine sound enhancement techniques to ...

Figure 5 - Man Machine graphical Interface (MMI) of R-sound Effect4.2 Sound design processThe Renault team clearly identifies 3 types of sound design processes for automotive sounds.- First one based on existing vehicles and engines- Second one based on expert’s knowledge and numerical simulations- Third one based on product intentionsThe main process is based on recording, analyzing, and then synthesizing an existing car and thenusing it to propose designed sounds. In this process, we focus on recognition of sound and accept afew modifications in order to keep it compatible with a majority of audio systems. The frequencycomponents in the final sound are similar to the recorded sound.This process leads to “rich components” as shown in figure 6. Rich component means that thespectrum is composed of many orders and each order level varies very quickly with engine speed.Figure 6 - typical order analysis of sound obtained by measurementThe second sound design approach is based on theoretical harmonic creation. Engine expertsknow which engine order is generated by a specific architecture (V6, V8, L4 …). We use numericalsimulation to calculate each engine order level for each RPM, from mobile masses efforts andcombustion force. This approach leads to “pure component” spectrums as figure 7, each order levelis varying slowly as RPM changes and it presents less that 10 or 15 orders (more is possible forspecific engines). In our case we use this kind of sound design process to propose a motorcyclesound; as Renault is not a motorcycle manufacturer so we decided to propose a theoretical sound.Figure 7 - typical order analysis of sound obtained by an expert approachThe third sound design strategy is based on product intention and leads to a pure sound creation.We used this method to propose a specific sound for the space shuttle or a UFO that is clearlyimpossible to measure. We don’t have any in-house expert to design this sound, and the unique7