Abstract

Hearing in noise is a core problem in audition, and a challenge for hearing-impaired listeners, yet the underlying mechanisms are poorly understood. We explored whether harmonic frequency relations, a signature property of many communication sounds, aid hearing in noise for normal hearing listeners. We measured detection thresholds in noise for tones and speech synthesized to have harmonic or inharmonic spectra. Harmonic signals were consistently easier to detect than otherwise identical inharmonic signals. Harmonicity also improved discrimination of sounds in noise. The largest benefits were observed for two-note up-down "pitch" discrimination and melodic contour discrimination, both of which could be performed equally well with harmonic and inharmonic tones in quiet, but which showed large harmonic advantages in noise. The results show that harmonicity facilitates hearing in noise, plausibly by providing a noise-robust pitch cue that aids detection and discrimination.

Here you will find some sound examples demonstrating the phenomena described more fully in the paper.

Demo 1: Detection In Noise

This demo is best heard over headphones, set to a low volume.

In the first demo, we show that harmonic sounds are easier to detect in noise than otherwise identical inharmonic sounds.There are sample stimuli from the study, in which you will hear two noise bursts, one of which contains a tone.

In a second demo, you will hear continuous noise, with a 300ms tone approximately every 500ms. The onset timing of each tone is randomized in time to avoid priming. The dB SNR will decrease for each tone, and is matched for the Harmonic and Inharmonic demos - notice that you will be able to hear more tones clearly in the Harmonic case, compared to the Inharmonic case. The 14th tone (of 17) in the Harmonic case is close to the average detection threshold for participants, and in the Inharmonic case, the 11th tone is close to the average detection threshold.

Harmonic Trial	Inharmonic Trial	Pure Tone Trial

Harmonic Demonstration	Inharmonic Demonstration

Demo 2: Contour Discrimination In Noise

This demo is best heard over headphones, set to a low volume.

This demo shows that melodies composed of harmonic tones are easier to discriminate in noise than those composed of inharmonic tones. The melodies are comparably discriminable with no noise.