Room impulse response prototyping using receiver distance estimations for high quality room equalisation algorithms

TL;DR

This work tackles room equalisation under reverberant conditions by moving beyond single-RIR inversion to a prototype RIR that captures spatial variation. It introduces a receiver-distance estimation method based on a two-source triangle geometry to derive coordinates from TOA measurements and uses these distances to compute a frequency-dependent prototype via a weighted average, where weights factor both distance from the optimal listening position and loudspeaker directivity modeled by a spherical head model. The method yields a prototype impulse response $H_p(\omega)$ computed as $H_p(\omega) = \frac{1}{R} \sum_{r=0}^{R-1} \sqrt{|H_r(\omega) W(\omega,z_r,\theta_r)|}$ with $W(\omega,z,\theta) = W_{dist}(z) W_{freq}(\omega,\theta)$ and $W_{dist}(z)=(z+\delta)^\zeta$, where $z$ is the distance between the optimal and external receivers and $\theta$ encodes the azimuthal dependence; $z$ is determined from $z = \sqrt{(y_{opt}-y_{ext})^2+(x_{opt}-x_{ext})^2}$. Simulations show the Weighted prototype reduces spectral deviation at the optimal listening position by about 0.2 dB and maintains near-unchanged performance across the listening area, with statistically significant improvements ($p<0.05$) over unweighted methods. The approach is supported by an efficient distance-estimation technique and tunable parameters $\delta$ and $\zeta$ that trade off local accuracy and spatial robustness, offering a practical path to more robust room equalisation in real rooms.

Abstract

Room equalisation aims to increase the quality of loudspeaker reproduction in reverberant environments, compensating for colouration caused by imperfect room reflections and frequency dependant loudspeaker directivity. A common technique in the field of room equalisation, is to invert a prototype Room Impulse Response (RIR). Rather than inverting a single RIR at the listening position, a prototype response is composed of several responses distributed around the listening area. This paper proposes a method of impulse response prototyping, using estimated receiver positions, to form a weighted average prototype response. A method of receiver distance estimation is described, supporting the implementation of the prototype RIR. The proposed prototyping method is compared to other methods by measuring their post equalisation spectral deviation at several positions in a simulated room.

Figures (3)

• Figure 1: Example of a two source and receiver triangle (Black/Light Grey), and sub triangle (Grey) for acoustic receiver coordinate estimation
• Figure 2: Spherical Head Model frequency responses with varying azimuth angles, normalised so the on-axis response is flat.
• Figure : Room Diagram