🗊Презентация Small Concert Hall. Acoustics

Small Concert Hall Acoustics Application Gallery #20145

Abstract In this model the acoustics of a small concert hall, with a volume of 422.5 m3, are analyzed using the Ray Acoustics physics interface. The model shows how to: Set up a “microphone” in order to calculate the pressure impulse response and energy impulse response. (Physics Setup 1 slide) Set up an omnidirectional sound source containing one Fourier component (one frequency f0). (Source slide) And an omnidirectional source containing a frequency distribution (20 frequencies in the 1000 Hz octave band). (Source slide 2) Set up the basic boundary conditions for specular and diffuse scattering including absorption (Wall slides) Use the Sound Pressure Level Calculation feature (sub feature to the Wall) to determine the sound pressure level distribution at the seating area. Compare the energy response to simple room acoustics measures. (Results slides) Set up variables to sum and analyze the impulse response of the source emitting a frequency distribution.

Ray Acoustics Interface The Ray Acoustics physics interface is used to compute the trajectories, phase, and intensity of acoustic rays. Ray acoustics is valid in the high-frequency limit where the acoustic wavelength is smaller than the characteristic geometric features. The interface can be used to model acoustics in rooms, concert halls, and many outdoor environments. The properties of the media in which the rays propagate can change continuously within domains or discontinuously at boundaries. At exterior boundaries it is possible to assign a variety of wall conditions, including combinations of specular and diffuse reflection. Impedance and absorption can depend on the frequency, intensity, and direction of incident rays. Transmission and reflection are also modeled at material discontinuities. A background velocity may also be assigned to any medium.

Geometry

Definitions: Selections Set up selections for the different boundaries

Physics Setup 1

Physics Setup 2

Source 1: Release from Grid

Source 2: Release from Grid

Wall: Specular Reflection

Wall: Diffuse Scattering

Wall: Mixed Specular and Diffuse

Study 1 and 2

Study: Ray Tracing

Results 1 (Single Frequency)

Results 2 (Single Frequency)

Results 3 (Single Frequency)

Results 4 (Single Frequency)

Results 5 (Single Frequency)

Results 5 (Single Frequency)

Results 1 (Frequency Distribution)

Results 2 (Frequency Distribution)

COMSOL Ray Tracing Formulation The Ray Acoustics interface uses a mixed time and frequency formulation. This means that each ray has a specific frequency, it represents one Fourier component of the source signal. The propagation of each component is modeled in time. In the present model we only solve for one frequency. You can release multiple frequencies at once defined in different ways. The ray propagation is modeled by solving a set of ordinary differential equations (ODEs). Hamilton’s equation in the high frequency limit for wave propagation. This formulation of the ray problem allows for a detailed description of boundary conditions. The boundary absorption (impedance or reflection coefficient) can be dependent on both frequency and angle of incidence. The following auxiliary dependent variables are computed along each ray: the intensity, the phase, and the frequency.