Discrimination functions: can they be used to classify singing voices?

Area of Science:

• Acoustic phonetics
• Psychoacoustics
• Music perception

Background:

• Acoustic features for identifying singing voice categories and individual singers are sought.
• Listener perception of singing voice categories and individual voices is under-examined.
• Vocal timbre is studied for systematic variation between categories but assumed invariant within a singer.

Purpose of the Study:

• To test the assumption of invariant vocal timbre within an individual singer.
• To investigate how listeners perceive vocal timbre across different pitches for individual singers.

Main Methods:

• Recordings of 4 singers (2 mezzo-sopranos, 2 sopranos) singing the vowel /a/ at various pitches (A3 to A5).
• Listeners identified the 'odd' stimulus in trials comparing two stimuli from the same singer at different pitches against one from a different singer.
• Stimuli varied across singers and pitches to assess timbre perception.

Main Results:

• Listener ability to identify the 'odd' singer varied significantly based on pitch differences.
• This pitch-dependent identification success challenges the concept of invariant timbre for individual singers.
• Perceived vocal quality is demonstrated to transform across a singer's vocal range and registers.

Conclusions:

• The traditional concept of invariant timbre for individual singers is inaccurate.
• Vocal timbre should be understood as dynamic, involving perceived quality transformations across pitch and register.
• Future research should consider pitch and register variations when analyzing singing voice characteristics.