H1-A3 is an acoustic measure used to quantify the breathiness of a voice. It is calculated by subtracting the amplitude of the first harmonic (H1) from the amplitude of the third harmonic (A3). A large value of H1-A3 indicates a breathy voice, which is caused by incomplete vocal fold closure. This incomplete closure results in a lower amplitude of the first harmonic and a higher amplitude of the third harmonic, leading to a larger value of H1-