TRIZ Innovative Solutions to be explored for NVH refinement of Vehicles

There are always technical contradictions faced by a Vehicle Integration Team while attempting NVH refinements! Softer engine rubber-mounts give maximum vibration isolation but may not be durable. Higher contact ratio gears reduce the transmission- whine but their teeth can become thinner & broken under high torque. Heavy acoustic insulation or stiffer body or a Tuned Mass Damper would increase quietness inside the cabin but add to both weight and cost of the vehicle.

A more famous example of such contradiction is when the exhaust system designer has to compromise between

1. Sound Transmission Loss (STL)

2. Back pressure of the IC engine.

More the resistance offered to gas-flow thru' expansion chambers, reverse flow or perforated holes, STL would rise to reduce the Tail-pipe noise of the vehicle, but the engine would lose power to overcome this resistance unless a big silencer with costly glass-wool is used.

For all such conflict management, TRIZ, short for "Theory of Inventive Problem Solving," can be of a great help! It is a systematic approach developed in Russia by Mr Altshuller for creative problem-solving, emphasizing the identification of universal principles and patterns to

innovate solutions. This is a famous tool whose functioning is described widely over many years with 40 inventive principles used for 39 parameters of Contradiction.

An attempt is made by the Author here to apply this method for one of NVH problems; the below Tables should be self-explanatory for formulating it for the exhaust system:

TRIZ recommends various principles for brainstorming based on its databank; out of which Principle No. 35 of Parameter Changes looks more suitable.

Here, 2 opposite things need to happen on the same vehicle -- at the same time -- but for its 2 different features: the engine power rise and the exhaust tail-pipe noise reduction. Hence, the Separation principle on the Condition can be deployed while taking this Principle ahead:

This gives a clue to solve the conflict with the use of a valve in one of pathways of the exhaust hot pulsating gas flow. The valve will be closed at low or mid or steady high speeds where the engine power is not in full demand. This will give a desired reduction in both Pass By Noise (exterior) and overall in-cab noise.

On the other hand, the valve will open and reduce the back-pressure of the engine whenever the vehicle needs the full engine-power either on gradient or at high speeds or during overtaking !

The NHP exhaust system deployed a long back in 2005 assured the best of both worlds for Porsche 987: a quiet mode for those cool & relaxed drives and open the valves for an aggressive sounding exhaust---with a simple push of a wireless remote!

In a similar way, there could be many more such creative solutions to, not only, this exhaust system for ICE powered vehicles, but also, for other subsystems in the Automotive NVH world including EVs or Hybrid vehicles (facing the conflicting requirements) if various advanced TRIZ process tools are applied by a Team of Innovators!