Purpose: The aims of this study were to analyze and characterize the irrintzi (a folkloric shout emitted in a single breath used by the Basque people) acoustically and to describe the mechanism by which it is emitted. Method: Thirty-six sound samples of 12 female volunteers were analyzed. Acoustic analysis included primarily fundamental frequency (fo), spectral analysis in the time domain with a narrowband filter, and the use of linear predictive coding (LPC). Laryngeal and pharyngeal movements while emitting an irrintzi were studied by fiberoptic nasal endoscopy. Postural and mandible movements were observed and video recorded. Movements of the larynx and the vocal tract were also studied by lateral pharyngo-laryngeal radioscopy. Results: The central part of an irrintzi spectrogram contains a peculiar, repeated M-shaped motif unseen in the spectrogram of any other human vocal emission, and intensity was over 90 dB SPL in all cases. fo was very high (1487 Hz) especially at the end of the irrintzi. Fiberoptic nasal endoscopy consistently revealed considerable elevation of the glottis, with the larynx swinging forward and retraction of the ventricular bands. Lateral radioscopy showed a very high larynx and a high tongue dorsum. Conclusions: The irrintzi is a sound emitted in a single breath and characterized by its shrillness and loudness, qualities that make it audible in noisy environments and over large distances and the vocal technique observed when it is produced can be explained by the Estill voice model (Steinhauer et al., 2017). The use of this technique may help in the treatment of voice disorders and improve efficiency in singers, teachers, actors, and people who use their voice at high volume or at high frequency.