Experiments on tone adjustments

Many technical sounds contain tonal components originating from rotating parts, such as electric engines or tire/road noise. These are often considered to be more annoying than sounds without tonal components. Thus it is important to consider tonal components when assessing noise pollution. Several standards include sections dedicated to the assessment of tonal components in sound. These have in common that the magnitude of the tonal foreground is estimated relative to the noise background (e.g., tone-to-noise ratio, prominence ratio). In some standards, the higher annoyance of sounds containing tonal components is addressed by making a tone adjustment, i.e., by adding a few decibels to the measured sound level. The present study focusses on the German standard DIN 45681, where the tone adjustment increases with tone-to-noise ratio. The aim was to assess the tone adjustment in an adaptive matching experiment. First, the individual masked threshold of the tonal component was measured. Then a noise alone was adjusted to elicit the same loudness or preference as a mixture of tone and noise. The tone was added to the noise at different levels above the individual masked threshold. The results are compared to the tone adjustments calculated on the basis of the standard.