▁increased ▁ph on atory ▁effort , ▁and ▁vocal ▁fat igue . ▁There ▁may ▁be ▁a ▁sens ation ▁of ▁sor eness ▁or ▁pain ▁in ▁the ▁neck , ▁later al ▁to ▁the ▁l ary nx , ▁which ▁generally ▁occurs ▁because ▁of ▁the ▁increased ▁effort ▁needed ▁to ▁produce ▁the ▁voice . ▁ ▁Ac oust ic ▁signs ▁ ▁Major ▁ac oust ic ▁signs ▁of ▁vocal ▁fol d ▁nod ules ▁involve ▁changes ▁in ▁the ▁frequency ▁and ▁the ▁intensity ▁of ▁the ▁voice . ▁The ▁fundamental ▁frequency , ▁an ▁ac oust ic ▁measure ▁of ▁voice ▁pitch , ▁may ▁be ▁normal . ▁However , ▁the ▁range ▁of ▁pitch es ▁the ▁individual ▁is ▁capable ▁of ▁producing ▁may ▁be ▁reduced , ▁and ▁it ▁may ▁be ▁especially ▁difficult ▁to ▁produce ▁pitch es ▁in ▁the ▁higher ▁range . ▁The ▁intensity ▁of ▁the ▁voice , ▁an ▁ac oust ic ▁measure ▁of ▁amplitude ▁or ▁loud ness , ▁may ▁also ▁be ▁normal . ▁However , ▁the ▁individual ' s ▁amplitude ▁range ▁may ▁be ▁reduced ▁as ▁well . ▁P ert urb ations ▁or ▁variations ▁in ▁frequency , ▁known ▁as ▁j itter , ▁and ▁in ▁amplitude , ▁known ▁as ▁sh immer , ▁may ▁be ▁increased . ▁ ▁Aer od ynamic ▁signs ▁ ▁If ▁the ▁nod ules ▁affect ▁the ▁closure ▁of ▁the ▁vocal ▁fol ds , ▁air flow ▁levels ▁during ▁speech ▁may ▁be ▁increased ▁in ▁comparison ▁to ▁the ▁speaker ' s ▁habit ual ▁levels . ▁However , ▁air flow ▁levels ▁may ▁still ▁fall ▁within ▁the ▁upper ▁limits ▁of ▁the ▁normal ▁range . ▁The ▁degree ▁to ▁which ▁an ▁individual ' s ▁air