Investigation of the seat-dip effect using finite-difference time-domain simulations

Area of Science:

• Acoustics
• Architectural Acoustics
• Computational Acoustics

Background:

• The seat-dip effect (SDE) is a phenomenon where low-frequency sound absorption occurs in the seating areas of performance venues.
• The complex interplay of various seating configurations makes the underlying physical principles of SDE not fully understood by acousticians.

Purpose of the Study:

• To investigate the seat-dip effect (SDE) in performance spaces.
• To quantify the impact of geometric properties of seating areas on SDE using computational modeling.
• To identify key geometric factors influencing SDE and low-frequency sound propagation.

Main Methods:

• Utilized the finite-difference time-domain (FDTD) method for acoustic simulations.
• Employed three parameterized hall models to simulate numerous seat configurations.
• Analyzed the spatial and time-frequency evolution of sound within the simulated halls.

Main Results:

• Seating inclination (step size) and under-seat opening (underpass) significantly influence SDE.
• Stage height and sound source position were found to have a lesser impact on SDE.
• An underpass larger than the step size effectively mitigates the primary 80-100 Hz frequency dip across different hall types.
• The SDE is most pronounced in the early stages of the room's acoustic response.

Conclusions:

• Seating geometry, specifically step size and underpass dimensions, are critical determinants of the seat-dip effect.
• Strategic design of the underpass relative to the step size can control low-frequency sound absorption.
• The findings provide valuable insights for optimizing acoustic design in performance spaces to manage low-frequency response.