KEY POINTS:
Helen Clark's boast that she has a "voice advantage" over John Key in a vigorous debate is backed by teachers of speech.
The Prime Minister said after the first Leaders' Debate that Mr Key was trying to "shout me down". But she said he could not do that because " ... by women's voices I have a lower register, by men's voices he has a higher one".
Auckland voice coach David England said Helen Clark did indeed have an advantage.
"Anyone does who has a lower voice that's produced from the diaphragm, because that's where the power comes from," said Mr England.
"They both have good qualities but she has more of a diaphragmatic voice and he has more of a head voice."
Mr England said Mr Key's voice was not unduly high and he compensated with good projection and enthusiasm.
"He has quite good expression in his voice when ad libbing in a debate. However, in the House he can lapse into a monotone when reading a prepared speech."
Auckland Speech and Drama School director Simon Angelo said men's voices were generally stronger.
"Helen Clark has a particularly strong voice while John Key has a weaker voice and a strong South Island accent.
"With her lower tone coming from the whole chest, she has a little more bellowing power, I suppose."
How low was Helen Clark's voice on the register?
Mr England: "If she was a singer she would be described as a contralto, or alto, which is the lowest women's voice."
