Low-frequency Noise Reduction for Rotor Blade

NineSigma, representing a global trillion-yen sales manufacturer, seeks noise-reduction technology for low-frequency noise generated during the rotation of rotor blades, such as those of multicopters. Particularly, our client would like effective noise-reduction technology to reduce noise synchronized with rotation frequency.

Noise during the rotation of rotor blades attached to rotorcrafts such as helicopters and multicopters:

• Sound pressure level: approx. 95 dB at a height of 30 m
• • Frequency Band: ≤150 Hz
• Details of rotor
  • Rotor diameter: 4 m
  • Number of blades: 2
  • Rotation speed: 1000 rpm
  • Thrust: approx. 300 kg

Technological requirements

• Capable of reducing the sound pressure level by ≥5 dB at the primary and secondary components of blade passing frequency (BPF)
• Achieving a ≥10 dB reduction in overall sound pressure level (OASPL)

The Client expects technological approaches such as the following, but is open to others:

• Mechanism that produces less machine and aerodynamic noise
• Design of blade shape that prevents turbulent flow
• Sound absorbing coating on blades
• Device that actively control vibrations

The following technologies are not of interest:

• Noise-reduction technology inapplicable to rotor heads or rotor blades
• Proposal with simulations only
• Noise-reduction technology based only on conventional active flap control

The client engages in the development of noise-reduction technology for rotorcrafts such as multicopters and unmanned aerial vehicles (UAV). While the growing use of rotorcrafts is expected in the future, noise reduction has become a challenge. Particularly, low-frequency noise is concerned about an adverse effect on the human body, but there are few effective measures available now. The Client has been developing and exploring technologies mainly inhouse and in collaboration with known suppliers, however, they have not yet identified promising technology that can meet these needs. The client has therefore decided to recruit this technology in order to further accelerate research and development.

Proposal shall have clear points and should not include confidential information. Supplemental files may be submitted in addition to the proposal.

The client will evaluate all responses with the following criteria.

• Overall scientific and technical merit
• Approach to proof of concept or performance
• Economic potential of concept
• Realism of the proposed plan (action items, timeline, roles, deliverables, cost estimation)
• Potential for proprietary position
• Respondents’ capability and related experiences

After the submission due date, the client will review all submitted proposals. NineSigma will send the review results to each proposer 6-8 weeks after the due date. The client possibly asks clarifying questions before selecting the most suitable candidates for collaboration. The client will select best candidates through evaluations. During the selection process, the client may execute NDA with selected respondents, seek further information disclosure, and discuss specific development targets or potential opportunities.

The client will execute necessary agreements with the selected respondents and move to the advanced development phase. Specifics of any collaboration will be determined through consultation with the concerned parties.