Annoyance due to discrete tones in broadband background noise. Part 1: Experiments

Three experiments are described in which subjects judged the annoyance of various stimuli on a scale of 0 to 9. The stimuli comprised three broadcast noises, presented at various levels from 20 to 55 dB(A), to which pure tone were added at four levels above the respective masked threshold ranging from 5 to 26 dB sensation level; the broadcast noises were also presented on their own as a baseline for interpreting the annoyance judgements on the combination stimuli. For each combination, the effect of the tone was determined as a 'penalty', equal to the increase in level of the broadcast noise component on its own required to elicit the same annoyance as the combination. The tests were conducted in several sessions in anechoic binaural listening conditions with the exception of one series carried out in a simulated domestic living room; the change in environment was not found to influence the results. The tone penalty was found to increase nearly linearly with sensation level of the tone, and also to increase with tone frequency over the range 0.15 to 4.8 kilo-Hz, save for a local minimum at 1.2 kilo-Hz. The tone penalty also decreased at a mild exponential rate with the absolute level of the broadband noise component. The effect of varying the spectrum of the broadband noise was found to interact with the tone frequency. A general formula relating tone penalty to the variables will be presented in a companion report.