Noise reduction in a launch vehicle fairing using actively tuned loudspeakers

Area of Science:

• Acoustics
• Aerospace Engineering
• Control Systems

Background:

• Launch vehicle fairings experience damaging low-frequency, reverberant noise.
• Passive acoustic absorbers are difficult to implement due to irregular geometry and changing payloads.
• Real-time tuning of acoustic absorbers is necessary for effective noise reduction.

Purpose of the Study:

• To develop and validate a method for real-time tuning of loudspeakers as acoustic absorbers.
• To significantly reduce targeted, high-intensity, low-frequency acoustic modes within a launch vehicle fairing.
• To adapt loudspeaker dynamics to the non-ideal and changing environment of a launch vehicle fairing.

Main Methods:

• System identification techniques were used to determine the dynamics of the launch vehicle fairing.
• A control law was designed using a loudspeaker model as a reference.
• The control law tunes the dynamics of a non-ideal loudspeaker to function as an optimal tuned absorber.
• Experimental validation was conducted with a tuned loudspeaker in the fairing's nose cone.

Main Results:

• The tuned loudspeaker significantly reduced acoustic energy within the fairing.
• Experimental results confirmed the effectiveness of the real-time tuning method.
• The study verified simulation calculations for acoustic energy reduction.
• The system demonstrated successful adaptation to the complex fairing environment.

Conclusions:

• Real-time tuned loudspeakers are a viable solution for mitigating low-frequency noise in launch vehicle fairings.
• The developed system identification and control strategy effectively transforms non-ideal loudspeakers into optimal acoustic absorbers.
• This technology offers a promising approach to enhance acoustic environments within aerospace structures.