An electronic control unit mounted beneath the instrument panel takes input from engine sounds, including varying engine speed, vehicle speed and throttle position and generates augmented sound through an actuator. It is entirely separate from audio system, so there’s no reduction in music fidelity.

Features of the acoustic design

To perform this acoustic design, we viewed the engine as the generator of sound and the automobile as a medium for conveying sounds from one place to another. We then came up with an idea for how to achieve a smooth interaction between drivers and vehicles, and it was adopted.

The Lexus LFA is powered by a 10-cylinder engine that was co-developed by Yamaha Motor and has an even firing interval. Only physical acoustic methods were utilized to give the driver a direct sensation of this engine’s characteristics. There is no electrical or electronic sound processing. As a result, sounds that reach the driver are clear, dynamic, and smooth.

Furthermore, this acoustic approach has two advantages. The first is the ability to hold down noise under normal driving conditions, such as in a city. The other advantage is an outstanding response in engine sound during strong acceleration.

From the Lexus LFA Press Release:

- The superb acoustics of the LFAs V10 engine have been acoustically tuned to deliver a unique and Formula 1-inspired soundtrack
- Horizontally split intake surge tank mimics the acoustic chambers of wind and string instruments for a rich and resonant bass
- Tuned large diameter, equal-length exhaust manifolds run through dual exhaust pipes with a lightweight titanium dual-stage main silencer
- Motorsport-inspired main silencer features valve-actuation and lightweight titanium construction
- Three acoustically optimised sound channels ensure the LFAs cabin is filled with the engines sonorous intake and exhaust soundtracks.

The Lexus LFA is a car with relentless power delivery and an accompanying exhaust note to give you goose bumps, enthuses its chief engineer Haruhiko Tanahashi. He and his team have enhanced and fine tuned the acoustics of the LFAs ground-breaking V10 powerplant to deliver an awe-inspiring soundtrack from idle note to red-line wail - for those both inside and outside of the cabin.

The LFAs acoustic team studied the unmistakable soundtrack generated by a Formula 1 car at maximum revs. By emphasising the secondary combustion frequency of the LFAs engine and then introducing primary, secondary and tertiary firing harmonics, Tanahashi and his team created a signature exhaust note unlike that of any other road car.

This incredible soundtrack that significantly enhances the sensation of acceleration and speed was only made possible by meticulously tuning the LFAs multi-stage exhaust system. The left and right banks of the engine feature separate, equal-length, large diameter exhaust manifolds that not only enhance high-rev torque levels but also create a crisp and harmonious sound quality. After exiting the catalytic converters, the separate left and right exhausts flow through a smaller silencer box and then into the main multi-stage silencer housed behind the rear transaxle gearbox.

The main silencer features lightweight titanium construction, and employs a valve-actuated, dual-stage structure that channels exhaust flow according to engine speed. At 3,000 rpm and below, the exhaust valve remains closed to route the exhaust through multiple chambers for an unobtrusive exhaust note. Above this threshold, the valve opens, letting the exhaust bypass the chambers, flow into a single resonance chamber and exit directly through the LFAs strikingly stacked trio of exhaust outlets.

As well as tuning the exhaust note, the V10s induction system was also modified to complement the engines acoustic qualities. The powerplants uniquely formed horizontally split resin surge tank mimics the acoustic chambers of wind and string instruments. In addition, the V10s primary air intake port is fashioned from porous duct material to generate bass to mid-range tones.

The engines induction and exhaust soundtrack are carefully channelled into the LFAs cabin. The main sound channel that pipes in the engines induction notes runs from the surge tank through into the cabin below the main dash panel. This is complemented by two further sound channels - the upper cowl opening and the lower reflector.

The upper cowl opening, positioned at the top of the dash structure, is mainly responsible for piping mid- to high-range tones directly into the cockpit, while the lower reflector at the base of the cabin envelopes the LFAs occupants in rich and resonant engine notes. Along with the primary sound channel, these two acoustic enhancers ensure the driver sits at the center of what the LFA team call the 3D Surround Sound Concept a stirring soundscape that also acts as a constant aural reminder of the engines performance.