How is Honda's engine sound created? An NVH engineer discusses the source of its character

In Honda's engine development, NVH engineer Takatoshi Tatsumi, who is responsible for crafting the "character" and engine sound that riders feel, shared his development philosophy. He explains that sound design is not just about the exhaust system, but is designed from the engine's combustion itself.

Sound creation starting from combustion and final judgment based on human senses

In Honda's engine development, NVH engineer Takatoshi Tatsumi, who is responsible for crafting the "character" and engine sound that riders feel, shared his development philosophy. According to Tatsumi, what a rider perceives first is the sensation of combustion during the intake stroke, which forms the foundation of the engine's character. He states that this "pulse feel" cannot be created artificially and must be generated from the combustion of the engine itself.

While digital simulation is heavily used in modern development, the final judgment is left to human senses. It is evaluated not only by sound frequency and volume, but also by whether it matches the overall vehicle concept and how it sounds to the rider and those around them. Furthermore, NVH engineers are involved from the early stages of development, determining ignition timing and valve timing.

The role of internal structure and exhaust systems in bringing out the individuality of each model

Even models that use the same base engine are given different characters by changing specifications such as the cams. For example, in the CB1000F, a unique sense of pulsation is created by adopting 50mm intake ports for the 1st and 2nd cylinders and 40mm for the 3rd and 4th cylinders, and offsetting the valve timing by 17 degrees.

The exhaust system basically functions as a silencer, and its role is to highlight the engine's original character by suppressing unnecessary frequencies. It does not fake sound through electronic control; it merely draws out the sound that exists in the combustion process. In the 2023 CB750 Hornet and XL750 Transalp, which Tatsumi cites as models he is particularly proud of, a pulse feel that accompanies rising RPMs is achieved by tuning the dual tailpipes to different frequencies.

Various exhaust systems of current models