The harmonics‐to‐noise ratio applied to dog barks

In this paper a parameter is introduced to animal bioacoustics which is commonly used in human phoniatrics—the harmonics‐to‐noise ratio (HNR). It is a ratio of the acoustic energy of the harmonic components to that of the noise. Barks of domestic dogs are short, loud, and broadband utterances. The rationale for this method is that the acoustic wave of a barking call is characterized by the ratio of harmonic and noise components. Fifty barks from each of ten adult dogs (dachshound) uttered during a mild threat were considered. The HNR is estimated as follows: a 50‐ms time segment from the middle of the call is Fourier transformed (sampling frequency 30 kHz, 512‐point Hanning window). A ten‐point moving average curve was calculated from the spectrum. The maximum difference between the spectrum and the moving average is used as HNR. Two test persons were asked to arrange the barks of the ten dogs according to their personal perception of hoarseness. The measured HNR agrees perfectly with the perceived ordering. In one dog’s barks the HNR were measured twice to test the robustness of the procedure. A paired t‐test showed no significant differences between the two samples. This exemplifies that the relatively simple HNR is valuable in animal bioacoustics.