Yamaha get amped up: New MT-09 gets an intake amplifier to enhance the riding soundtrack

Yamaha have taken steps to make sure their MT-09 naked models make the best sound possible – for the rider, at least. Like exhaust fumes, noise emissions are closely monitored and limited under Euro5, impacting not only the design of exhausts but also intakes and engine covers as designers bid to muffle unwanted sound. 

Socially responsible? Absolutely. But there’s no denying that the sound of a bike’s engine is an important source of riding pleasure, and rarely more so than when that engine is a warbling triple like the 890cc CP3 motor in Yamaha’s 2024 model MT-09 naked range.

Intake noise is often more appealing than exhaust sound and Yamaha have now made a move to boost the amount of it that reaches the rider by using a patent-applied-for intake amplifier that focuses that sound directly at you without increasing the outright noise levels on their MT-09.

Speaking about the 2024 model, a statement from the company said: “Following the Jin-Ki Kanno philosophy to stimulate the rider’s senses and make them feel at one with the bike, sound was an important consideration in the latest EU5+ CP3 engine.

“The new MT-09’s sound is further amplified by a revised airbox featuring two newly designed air-intake ducts, which accentuate the high frequency sounds while maintaining a linear throttle response.

“This sound is then emphasised, especially at higher speed and revs, by the introduction of a new acoustic amplifier grille on top of the bike, delivering the CP3’s vibrant note directly to the rider.”

That ‘acoustic amplifier’ is the basis of a patent application which illustrates the thinking that’s gone into the system.

Externally, the only clues to its presence are the plastic cover that surrounds the fuel filler and extends forward to the ignition key, and more noticeably the two metal grilles set into it, looking exactly like speaker covers. 

There are no speakers though. Those grilles are the visible exits of a convoluted passage that leads directly to an opening in the top of the airbox, allowing the noise from the intake to be channelled out, directing it straight up through the grilles towards the rider without increasing outright volume.

Although a simple idea, the execution is made more complex because it’s essential that while airbox noise is allowed out through the grilles, water mustn’t be able to reach the airbox through them. 

To prevent that, a thin section of the fuel tank itself extends forward, in front of the fuel filler, and separates the grilles from the airbox intake. Sound can travel forward, around this shielding section, and then back again to the grilles, but water entering through the grilles can only go forward over the tank and then drop down through an opening at the front, without being able to travel back to the airbox. 

Even the thickness of the shielding is tuned to absorb some frequencies while allowing others past, ensuring the noise through the grilles is particularly pleasing.

Yamaha MT-09 air intake amplifier in detail

• Noise escape: The airbox, situated under the front of the fuel tank, has an opening in the top that allows air in and noise from the intakes out.
• Listen up! The sound waves are routed forward, around the front edge of the fuel tank, and then back under the plastic section on top of the tank to the grilles that face the rider.
• Waterproofing: A separate partitioning section is mounted between the upper cover and the fuel tank, it has two outer channels underneath the grilles, passing noise and water, and two inner ones, used for wiring.
• Getting grilled: Water that gets in through the sound grilles on top of the tank is channelled forward through the channels but then drops straight down through an exit at the front of the tank and can’t get back to the air intake on the top of the airbox.
• Fuel tank thickness: The thickness of the fuel tank between the grilles and the airbox is tuned to absorb unpleasant frequencies but allow more welcome ones to reach the grilles.