Let’s Talk Sound Frequencies!
The Highs and Lows of Sound Frequency
To most of us, it’s a miracle, and one thing is true: Few understand how we come to hear the sounds of our daily lives. If you’re feeling like you’re missing out, here is an easy-to-understand introduction of sound frequency to get you started.
Sound waves travel through air, water and even the ground. Once they reach our ear, they cause the delicate membranes in our ears to vibrate, allowing us to hear the voices of our loved ones, listen to our favorite music or the calming sounds of raindrops on a tin roof and the distant sound of thunder. Admittedly, this is a rather simple explanation of a complex process.
Sound frequency is an important aspect of how we interpret sounds, but it is not the only one. A sound wave has five characteristics: Wavelength, time-period, amplitude, frequency and speed. While amplitude is perceived as loudness, the frequency of a sound wave is perceived as its pitch.
The higher the frequency waves oscillate, the higher the pitch of the sound we hear
As you see, sound frequency is determined by the way in which sound waves oscillate whilst travelling to our ears, meaning that they alternate between compressing and stretching the medium, which in most cases is air. In the same medium, all sound waves travel at the same speed.
Squeaky sounds, like the blow of a whistle or a screaming child, oscillate at a high frequency, resulting in oftentimes deafening high-pitched sounds. The low rumbling of a nearing storm or a bass drum, on the other hand, is produced by low-frequency oscillation, so we hear it as a very low-pitched noise.
Measuring the Frequency of Sound
How is sound frequency measured? The total number of waves produced in one second is called the frequency of the wave. The number of vibrations counted per second is called frequency. Here is a simple example: If five complete waves are produced in one second then the frequency of the waves will be 5 hertz (Hz) or 5 cycles per second.
Also called infrasound, low-frequency sounds stand for sound waves with a frequency below the lower limit of audibility (which is generally at about 20 Hz). Low-frequency sounds are all sounds measured at about 500 Hz and under.
Here are a few examples of low-frequency sounds:
- Severe weather
A high-frequency sound is measured at about 2000 Hz and higher.
- Computer devices
- Glass breaking
- Nails on a chalkboard
Are Intensity and Frequency of Sound the Same?
The answer to this question is clearly no. You might suspect, that the higher the frequency, the louder we perceive a noise, but frequency does not tell us how loud a sound is. Intensity or loudness is the amount of energy of a vibration and is measured in decibels (dB). If a sound is loud, it has a high intensity. Learn more about measuring the daily noise of our lives in decibels here.
What is the Hearing Threshold?
Healthy young adults should be able to hear frequencies anywhere between 20 and 20.000 Hz. The most important frequencies for speech and language are between 250 and 8000 Hz. What we call the hearing “threshold” is the lowest intensity where a person begins to hear a sound. Normally, this threshold for loudness is between 0 dB and 20 dB. But the hearing threshold of sound frequencies varies from one individual to another. This explains why you might hear a noise from a near construction site or the neighbors down the street, but your friend does not.
Frequency Hearing Loss
One of the most common types of hearing loss is caused by aging: For many people, high-frequency sounds are becoming harder to hear as their age progresses. It can affect anyone of any age but is common in older adults, as well as people exposed to loud noises.
Sometimes high-frequency hearing loss is hard to identify as affected people can follow normal conversations, but will experience trouble hearing certain consonants (such as s, h or f), which are spoken at a higher pitch. To those experiencing this type of hearing loss, words may sound muffled, especially over the phone or tv or when spoken by women and children.
What causes this change in hearing ability?
High-frequency hearing loss occurs when the tiny sensory hearing cells in the inner ear are damaged through loud and extended noise exposure, strong antibiotics, certain diseases, tumours, and of course, the natural decline caused by age.
The so important tiny hair cells are responsible for translating sounds into electrical impulses, which the brain interprets as recognisable sound.
Why is high-frequency hearing loss more common than low-frequency hearing loss?
As the lower part of the inner ear translates high-frequency sounds and lower-frequency sounds are perceived by the hair cells at the top and damage normally occurs from the bottom up, higher-frequency sounds are impacted first.
How to Identify Frequency Hearing Loss
Both high and low-frequency hearing loss can easily be identified with a hearing test. If you think that you or a loved one may be suffering from any type of hearing loss, you shouldn’t hesitate to contact a hearing care professional or take our quick online quiz that will help you determine whether a test is necessary or not.
There are many ways to test hearing. The most common are:
Behavioural testing in a sound booth
A child-friendly way to test hearing. Through headphones, the child hears a tone and presses a computer key, puts a piece in a puzzle or simply claps their hands. Most children will be assessed through a combination of physiological and behavioural tests.
Otoacoustic emission (OAE) testing
Your audiologist uses OAE tests to find out how well your inner ear, or cochlea, works. It measures otoacoustic emissions, short OAEs, which are sounds the inner ear makes when responding to a sound. If you have normal hearing, you will produce these OAEs. If your hearing loss is greater than 30 decibels, your inner ear is not able to produce these very soft sounds.
Auditory brainstem response (ABR) testing
Auditory brainstem response tests are less common but still conducted by many audiologists, especially when suspecting that your hearing loss could be caused by your auditory nerves or be rooted in a neurological disorder. During ABR testing, electrodes are placed around the head to measure the brain’s response to auditory stimuli.
A healthy adult should be able to hear frequencies anywhere between 20 and 20.000 Hz. The hearing ability can, however, be negatively affected by loud and extended noise exposure, strong antibiotics, certain diseases, tumours, and age. Hearing loss oftentimes is preventable. Protect your hearing by understanding how decibels and frequencies work.
If you’re already experiencing high or low-frequency hearing loss, adjusting to life with hearing impairment can be challenging. Read our guide to living with hearing loss and be prepared.