Psychoacoustical Estimation of Selected Acoustic Signals Which Can Be Applied at Pedestrian Crosswalks

Abstract

The paper presents a psychoacoustical evaluation of selected acoustic signals, which according to Polish and international recommendations can be applied at pedestrian crosswalks. The aim of the study was the optimal adjustment of parameters of the signals emitted at pedestrian crosswalks, and to meet the expectations of persons with vision impairments as well as nearby residents or workers working near the crossing. The psychoacoustical evaluation of acoustic signals consists of determination of the hearing threshold of signals in the quiet, detection of signals presented against a background of various types of traffic noises (estimated signal-to-noise ratio) and annoyance assessment of signals. Three types of intermittent sounds were analysed: signals with rectangular time pattern filled up with rectangular wave, signals with rectangular time pattern filled up with sinusoidal wave and signals with triangular time pattern filled up with sinusoidal wave. Four fundamental frequencies (550 Hz, 880 Hz, 1580 Hz and 2000 Hz) and two repetition rates (5 Hz and 9 Hz) were tested. The results of the study have shown that the most suitable signals which can be applied at pedestrian crosswalks are the intermittent sounds with rectangular time pattern filled up with rectangular wave of fundamental frequencies 880 Hz and 1580 Hz and repetition rate 5 Hz and the intermittent sounds with rectangular time pattern and triangular time pattern both filled up with sinusoidal wave of fundamental frequencies 1580 Hz and repetition rate 5 Hz.