A Short Tutorial on Sound Level and Loudness for Voice (Article)
With regard to fundamental frequency, sound level (SL) increases about 6 dB/octave, all else being equal. This is the primary reason why females often outsing males on the opera stage if they sing an octave higher. With regard to lung pressure, SL increases about 6-9 dB/with every doubling of lung pressure. The major phenomenon here is increase in peak glottal airflow. The frequency spectrum affects loudness perception if the sound is more than a simple tone. (posted 2:34 PM, August 27, 2014)

Constructing Exercises that Enhance the Management of the Interdependence of the Vocal Folds and Breath Management in Singing (Article)
It has long been the hallmark of a fine teacher to assign proper vocalises to the student. From a scientific perspective, the messa di voce, staccato and sustaining long phrases are discussed. (posted 2:34 PM, August 27, 2014)