Iva Salom

Multilayer graphene condenser microphone

Vibrating membranes are the cornerstone of acoustic technology, forming the backbone of modern loudspeakers and microphones. Acoustic performance of a condenser microphone is derived mainly from the membranes size, surface mass and achievable static tension. The widely studied and available nickel has been a dominant membrane material for professional microphones for several decades. In this paper we introduce multilayer graphene as a membrane material for condenser microphones. The graphene device outperforms a high end commercial nickel-based microphone over a significant part of the audio spectrum, with a larger than 10 dB enhancement of sensitivity. Our experimental results are supported with numerical simulations, which also show that a 300 layer thick graphene membrane under maximum tension would offer excellent extension of the frequency range, up to 1 MHz.

Analysis of acoustical characteristics of a church bell sound

The question of how to define a pleasant sounding bell has been posed long ago, since the bell is one of the oldest musical instruments. Recent technological advances provide powerful tools for detailed acoustic analysis of bells. However, subjective aspect of a bell sound as a main indicator of a bell sound quality has been to a certain extent neglected. The main goal of this research was to determine correlation between objective and subjective characteristics of a bell sound.

An automated environment for hardware testing using PXI instrumentation and LabVIEW software

For the requisite of verifying the MIKME advanced microphone during serial production, an automated test system for hardware testing was developed. The system, that comprises a specially designed test fixture — bed-of-nails, the PXI instrumentation and a LabVIEW application, is presented in the paper with all of its features related to the MIKME product. The proposed solution is up to 20 times faster, significantly cheaper and much more reliable than manual testing.

Design and realization of FPGA platform for real time acoustic signal acquisition and data processing

This paper describes the realization of an FPGA platform designed for real time acoustic signal acquisition and data processing. The paper presents complete development process, starting from high level system design including signal integrity simulations to real system measurement results based on described platform. A real system for localization of the dominant noise source based on the platform is presented.

Evaluation of different AAC codec realizations for arm architectures

The paper presents objective and subjective evaluation of AAC audio codec realizations in relation to bit rate and resolution. Chosen audio material was coded and decoded using implementation provided by four different vendors and compared to the original audio clips by using EAQUAL software. Two realizations with highest scores were then compared using subjective A/B/X listening test. The different bitrates of the best evaluated codec were compared using A/B/X listening test as well. Finally, the optimal choices of codec and of bitrate were made both on subjective quality of the codecs and on other important objective parameters such as processor time and memory occupation of ARM architecture realizations.

Laboratory model for partial discharge diagnostics using acoustic emission measurement

One of the major causes of transformer failures is dielectric breakdown. Partial discharges cause gradual insulation degradation thus partial discharge activity monitoring provides transformer state insight. This paper gives an overview of common methods for partial discharges detection and source location in transformers, with special reference to the acoustic method as non invasive and interference resistant method suitable for application. For laboratory testing a model of a measuring system for acoustic emission measurement was developed.