Modeling the Intermodulation Distortion of a Coaxial Loudspeaker

Authors: Dupont, Edward; Lipshitz, Stanley P.

Coaxial loudspeaker drivers are known to produce intermodulation distortion. In a simplified model, the woofer is treated as a baffled planar piston and the tweeter is treated as an acoustic monopole located in front. An integral solution to the second-order wave equation shows that the boundary effects dominate air nonlinearities. Several numerical investigations of the model were compared with experiments. Intermodulation products decrease as the tweeter is moved off axis.

Download: PDF (HIGH Res) (5.32 MB)

Download: PDF (LOW Res) (604.22 KB)

Investigations on an Early-Reflection-Free Model for BRIRs

Authors: Menzer, Fritz; Faller, Christof

Simulating the late reverberation of a room using a synthetically generated reverberation tail is a common practice in the design of artificial reverberators. Binaural reverberators could benefit from better knowledge of the perceptual cues that are relevant for the reverberation tail. In this study the use of filtered white Gaussian noise instead of the original tail was subjectively evaluated. Matching the interaural coherence in each frequency band produced better results than full-band matching. In some cases time-dependent matching improved quality. Results are based on subjective studies.

Download: PDF (HIGH Res) (1.41 MB)

Download: PDF (LOW Res) (407.59 KB)

Measurement System for Personalized Head-Related Transfer Functions and Its Verification by Virtual Source Localization Trials with Visually Impaired and Sighted Individuals

Authors: Dobrucki, Andrzej; Plaskota, Przemyslaw; Pruchnicki, Piotr; Pec, Michal; Bujacz, Michal; Strumillo, Pawel

Creating personalized head-related impulse responses is critically important for visually impaired people using electronic travel aids. This study demonstrates an efficient means of generating responses for thousands of locations in about 10 minutes. Verification trials, which measured listeners’ ability to accurately locate virtual sound sources, had average errors in azimuth ranging from 9 to 24 degrees. Such accuracies are sufficient for implementing obstacle sonification for travel aids.

Download: PDF (HIGH Res) (17.44 MB)

Download: PDF (LOW Res) (423.35 KB)

Large-Signal Design and Performance of a Digital PWM Amplifier

Authors: Midya, Pallab; Roeckner, Bill

Improving the large-signal performance of digital pulse-width modulators effectively increases the maximum power capacity without increasing the power supply. To achieve higher efficiency, a number of features have been combined to produce a seamless transition between high-order noise shaping, which exhibits ultra-low noise, and a first-order loop, which has a theoretical maximum duty cycle of 100%. Variable-order feedback and variable-phase sampling enable the system to achieve high accuracy at duty cycles that range from zero to one. The overall system exhibits THD values of 0.01% at power levels almost twice that of similar closed-loop systems.

Download: PDF (HIGH Res) (14.1 MB)

Download: PDF (LOW Res) (350.74 KB)

Download: PDF (1.44 MB)

Loudspeakers and Rooms: The Low Down

Authors: Rumsey, Francis

[Feature] Loudspeakers and rooms interact to modify the frequency response of reproduced sound. Active and passive forms of correction can be employed either in the loudspeaker or the room, or both, that aim to improve the uniformity of the bass response over the listening area.

Download: PDF (946.74 KB)

Download: PDF (2.64 MB)

Download: PDF (834.64 KB)

Download: PDF (142.11 KB)

Download: PDF (128.41 KB)

Download: PDF (216.77 KB)

Download: PDF (216.77 KB)

Download: PDF (202.39 KB)

Download: PDF (112.78 KB)

Download: PDF (99.64 KB)

Download: PDF (31.83 KB)

Download: PDF (626 KB)

Download: PDF (721.58 KB)