Recent research at Duke University in North Carolina, USA has discovered that men with deeper voices make more money, run larger companies, and stay in their jobs longer. They are simply more successful.

Dr Yi Xu of University College London agrees, but also said that research shows that men prefer women with higher pitched voices suggesting they were submissive and petite. This seems to contradict the well-known ‘deepening’ of Margaret Thatcher’s voice to make her sound less shrill and instead give her more gravitas.

Last year there was an article showing that both male and female teachers with deeper voices had less trouble with pupils in the class in secondary schools. Who is right in this apparent contradiction? The first finding – deep male voices versus female voices is really about sexual attractiveness. But the general deepening of voices is, I believe, about power and persuasion outside anything to do with sex.

So how deep is a deep voice? We measure this using the Fundamental Frequency (also called F0), which is a measure of deepest voiced sound in the human voice. There are a series of harmonic frequencies above this, usually labelled F1, F2 etc. Each harmonic is at double the frequency of the one below it.

Pitch is measured in vibrations per second, or Hertz (shortened to the symbol Hz). For men, F0 is usually between 85 and 180 Hz, and for women it ranges from 160 to 255 Hz. To set this in musical context Middle C on the piano is 261.6 Hz, and is also known as C4. Two octaves down, we get the much deeper C2 at 65.4 Hz. C2 is indeed very deep and outside the speaking range of most men. The optimum F0 for men is around 100 Hz, and for women 190 Hz, according to our Associate, Dr Branka Zei of the Vox Institute in Geneva.

So back to the question: Why do deep voices, in both men and women, carry more weight in developing a more persuasive successful person?

I think there are two reasons. First a deep voice creates an image of power and size. We do not associate a deep voice with slight physique or weak character. But in reality, this is not true. Some Russian Basses can sing below Deep C2, but some of them are pint-sized. They’re easy to find and listen to on YouTube.

Second, a deep voice means a relaxed larynx, indicating calm and confidence. The opposite is easier to observe: Someone who is stressed, unsure or just plain nervous will constrict their larynx and so sound squeaky.

What can we do about this? Well, quite a lot as it turns out.

The frequency harmonics are easy to see:

But using the deeper frequencies of our voice is not enough. We have to modulate our pitch up and down and at the right times. We know that a rising tone signals discomfort, uncertainty, an incomplete thought or lack of confidence.

The first graph below shows a voice ending a phrase in a rising tone. Australians are famous for this, but once plugged into their accent we can still differentiate the difference between accent and uncertainty.

Below that we can see a falling tone which shows finality and a sense of conviction.

So what do we do if nature endowed us with a high pitched voice? A high tenor will never make it to deep bass. Likewise a high soprano will not become an alto, except with the ageing process where our voices fall in pitch.

The truth is that other factors become more important. The words that you utter, your body language are key components. Fluency, articulation, phrasing, use of silence all contribute. Tony Blair has quite a high pitched voice, higher than Gordon Brown, but it has done him no harm, perhaps as it is much more modulated.
All the same, the ability to use the deeper registers of your voice may just help you to get that pay rise!