A similar investigation is performed moving up in pitch until the patient produces the highest note they are capable of, regardless of volume. Typically this vocal ceiling is reached where the vocal cords, placed on a stretch, reach the limit of their ability to vibrate given their mass and stiffness, as well as the limit of energy that subglottic airflow can impart.
Moving upward several semitones at a time to assess the upper vocal range quality and determine the highest note. Usually, individuals become louder as they try to reach the highest notes.
When the uppermost notes have a tight quality, we could term this a muscle-quality vocal ceiling. There are other qualities possible for a vocal ceiling. The individual may reach a note where the voice suddenly cuts out and this can be suggestive of a swelling-quality vocal ceiling caused by a sudden dampening of vibrations when a swelling touches the opposite vocal cord or they might leak air at the highest note suggestive of a gap-quality vocal ceiling caused by a lack of closure.
Since most of us speak near the lower end of our vocal pitch range, there are more notes to assess as we move up in pitch.
I would roughly diagram a normal female moving up in pitch this way with the increaed volume represented near the top of the range.
The low-volume vocal ceiling will typically occur at a much lower pitch than a high-volume vocal ceiling.