Margaret Thatcher famously took voice coaching from The National Theatre and the result was a reduction of pitch of 46 Hz and a general slowing down of her delivery. Ultimately this was parodied, however a study by online journal, the Public Library of Science, found that both men and women prefer the voice of female leaders to be lower.
In business and situations of leadership, a deeper voice is associated with power. Adult males tend to speak at around 125 Hz while adult females at 200 Hz. Children tend to speak at between 250 and 400 Hz and babies cry at around 500 Hz.
A study by University College San Diego took speech samples from 792 CEOs from Standard and Poor’s 1,500 stock index and one of the conclusion was that CEOs with lower voices manage larger companies. A decrease in voice pitch of 22.1 Hz translated to an increase in assets of $440 million. They also found that CEOs with a lower pitched voice earned $187,000 a year more than those with higher voices.
Physical attributes which influence vocal tone include body size, laryngeal size and the length of the vocal tract and vocal fold, the part of the vocal system which vibrates. However, voices can be trained by vocal coaches and many people report that learning to sing can help develop a speaking voice.
However, pitch may not be the main thing that influences how audiences react to your speaking voice. A study by Stanford University found that 7 out of 10 people found a nasal voice annoying.
The problem with assessing your own voice is that what you hear inside your head is different to the actual sound of your voice to other people. You will also be so used to your own voice that you may not be able to make an objective assessment. The only way to do it is to ask someone who you trust to listen to your delivery and let you know. There are also professional organisations such as Toastmasters where peer assessment of your voice and other aspects of your speaking delivery will help you to improve.