Javier Gómez Bolaños

An optoacoustic point source for acoustic scale model measurements

A massless acoustic source is proposed for scale model work. This source is generated by focusing a pulsed laser beam to rapidly heat the air at the focal point. This produces an expanding small plasma ball which generates a sonic impulse that may be used as an acoustic point source. Repeatability, frequency response, and directivity of the source were measured to show that it can serve as a massless point source. The impulse response of a rectangular space was determined using this type of source. A good match was found between the predicted and the measured impulse responses of the space.

Beamforming with a volumetric array of massless laser spark sources--Application in reflection tracking.

A volumetric array of laser-induced air breakdown sparks is used to produce a directional and steerable acoustic source. The laser breakdown array element is broadband, point-like, and massless. It produces an impulse-like waveform in midair, thus generating accurate spatio-temporal information for acoustic beamforming. A laser-spark scanning setup and the concept of a massless steerable source are presented and evaluated with a cubic array by using an off-line far field delay-and-sum beamforming method. This virtual acoustic array with minimal source influence can, for instance, produce narrow transmission beams to obtain localized and directional impulse response information by reflection tracking.

Laser-induced acoustic point source for accurate impulse response measurements within the audible bandwidth

Laser induced air breakdown is proposed as a sound source for accurate impulse response measurements. Within the audible bandwidth, the source is repeatable, broadband, and omnidirectional. The applicability of the source was evaluated by measuring the impulse response of a room. The proposed source provides a more accurate temporal and spatial representation of room reflections than conventional loudspeakers due to its omnidirectionality, negligible size and short pulse duration.

Estimation of pressure at the eardrum in magnitude and phase for headphone equalization using pressure-velocity measurements at the ear canal entrance

A method for estimating the pressure at the eardrum in magnitude and phase is proposed. The method uses measurements of pressure and particle velocity at the entrance of the ear canal to estimate the product between the propagation constant and the length of the ear canal. This estimation of the ear canal properties is used then to estimate the pressure at the eardrum. The proposed method provides equal magnitude response to that obtained using the energy-based estimation method and similar phase to that of the pressure measured at the eardrum of an artificial ear. The method is evaluated for headphone equalization purposes. The results show that the proposed method provides similar equalization filters to those obtained with measurements at the eardrum of an artificial ear and with measurements at the entrance of a human ear.

Horizontal localization of auditory and visual events with directional audio coding and 2D video

The effects of using two-dimensional video projection together with parametric three-dimensional spatial audio reproduction system are examined in this study. The discrepancy between the auditory and visual events, and differing depth cues, are evaluated by means of subjective evaluations using the method of adjustment. The results show the Directional Audio Coding to be well suited for immersive audiovisual setups allowing a large area of viewing positions.