Audio and communications
ISVR Consulting's experience in audio and communications is wide and varied.
Some examples are:
- Measurement and assessment of noise exposures from headsets and earpieces in call centres and control rooms, and radio earpieces used by emergency services
- Choosing appropriate sound level for radio earpieces based on likely speech traffic for police and other emergency services
- Evaluating the response of a headphone sound limiter to audio signals with various spectra, durations, duty cycles and crest factors to prevent excessive exposure to noise but without sudden level changes that would affect sound quality for the user. Included developing a battery of tests to verify performance for the manufacturer.
- Measuring the Speech Transmission Index from the boom microphone of a flying helmet via an intercom to the earphones of a second flying helmet in a helicopter noise spectrum. The helmet manufacturer was required to demonstrate compliance with a customer’s specification
- Optimising the design of fire alarm sounders to increase the output sound level of tones and optimise the frequency response for intelligible spoken warnings using the Speech Transmission Index
- Measurements of frequency response, sensitivity, harmonic distortion, dynamic range and directivity of a remote area microphone for a cockpit voice recorder to demonstrate compliance with aviation regulations
- Revised design for the UK of warning sounds for the GSM-R railway radio system
- Assessing whether or not a train horn would be heard and recognised at a given distance by track workers using noisy tools and equipment as part of an accident investigation
- Design of an active noise control system for a mobile phone held against the ear
- Measurement of Speech Transmission Index using Brüel & Kjær Dirac software
- Calculation of the Speech Intelligibility Index, SII, (which replaces the Articulation Index) from one-third octave band measurements of speech and noise.