Speaking in noise: How does the Lombard effect improve acoustic contrasts between speech and ambient noise?

Active strategies were evidenced, but were subtle and of second order to the primary strategy of speaking louder: for each gender, fundamental frequency (f0) and first formant frequency (F1) were modified in cocktail-party noise in a way that optimized the release in energetic masking induced by this type of noise. Furthermore, speakers showed two additional modifications as compared to shouted speech, which therefore cannot be interpreted in terms of vocal effort only: they enhanced the modulation of their speech in f0 and vocal intensity and they boosted their speech spectrum specifically around 3 kHz, in the region of maximum ear sensitivity associated with the actor's or singer's formant.