The frequency of the human voice has a direct bearing on which type of hearing aid will best suit so it pays to know a little about this subject.
The human voice and the human ear are a precisely tuned set of instruments. Theoretically, the human ear can hear from 20 hertz (Hz) to 20,000 Hz, but is most sensitive in the range of 300 Hz and 3000 Hz; a person with normal hearing should be able to distinguish more than 250,000 separate sounds.
Experts question how many people actually can hear sounds above 16,000 Hz, however, and say that after age 40, everyone loses the ability to hear those higher frequency sounds.
The human voice also falls right into this range. Although the range varies between male and female, the normal conversational vocal range for humans is between 250 and 4000 Hz and this is the range that the hearing aid I use, the Acoustitone Pro is designed for.
“For speech clarity, you need to be able to hear between 2000 and 4000 Hz,” said Bart Baker, audiologist at the world-renowned Farrior Ear Clinic in Tampa, Florida (USA). “When you look at the hearing of someone with no hearing loss, typically there are no peaks or valleys; the range of hearing is flat all the way across the audiogram, and no one frequency is better than the others.”
Of course, everyone’s hearing loss is different, but when you buy a hearing aid, you’re getting an instrument designed to help your hearing loss in that range of human speech.
When you put a hearing aid in your ear, Baker said, you experience a phenomenon called “insertion gain” and “insertion loss.”
“This means that you gain some in the low frequencies and lose some in the high frequencies,” he said. “That amount of gain and loss varies from model to model, depending on the hearing aid. Whoever is fitting the hearing aid works with the patient to adjust that. Every company has ‘fitting formulas’ that take everything into consideration to come up with the best choice for the patient, particularly with programmable hearing aids.”
Baker explained that “fitting formulas” are provided by every manufacturer for each of that manufacturer’s specific hearing aid models.
“They calculate the needed amplification for the specific hearing loss,” he said. “The manufacturer may call it a formula or an algorithm. Their hearing aids are fitted based on their own formulas.”
Of course, that middle speech range is not the only thing you want to be able to hear. For instance, conversational frequencies are only part of the range of the human voice; the singing range is much broader. In addition, the frequency of our voices changes as we age.
Children, for example, have much shorter vocal cords than adults do. As a result, their voices are higher and lighter than mature voices. As children grow up, their voices settle into one of four categories, depending on whether they’re male or female, and on the shape and size of their vocal cords. Sopranos, the highest female voices, can sing in a range from 250 to 1000 Hz. Altos (or contraltos) sing in a range from 200 to 700 Hz. Tenors (usually men, but once in a while female) sing in a range from 110 to 425 Hz. And basses, the lowest of the low, range from 80 to 350 Hz.