Snoring sounds and their types

The sound of a snore can be assessed according to the vibration of tissue, which is also associated with the duration of sound. Soft palate vibration, for instance, typically produces the longest of all snores, followed by that which is produced from the base of the tongue and is known as an epiglottal snore.

Did you know? The average snore normally ranges between 60 and 80 decibels, which is about as loud as normal talking / conversation. There are several world record holders for the loudest recorded snores…

The Guinness Book of World Records recorded the decibel measurement of chronic snorer, Melvyn Switzer in June 1984. He set the then world record at 87.5 decibels – the equivalent of a diesel truck engine. ⁽²⁾ Anything louder than 85 decibels is considered to be in range of sound that could begin to cause damage to one’s hearing.

In the year 1993, Swede Kare Walkert topped that world record with one of her own – 93 decibels. If the sounds of a lawnmower has ever had you climbing the walls, this measurement is a close equivalent. ⁽³⁾

More recently, in 2009, Jenny Chapman was dubbed Britain’s loudest snorer, measuring a shuddering noise factor of 111.6 decibels. It is said that her snore is just a handful of decibels louder than what you would hear from a low-flying jet (around 103 decibels).

The biomechanical events that induce snoring are complex and highly variable, in fact, endoscopic observations of snorers while they sleep have revealed different modes of snoring in various individuals. ⁽⁴⁾ As a result, depending upon where the vibration occurs in the airways during snoring, the sounds produced by one snorer can be very different to those of another.

A snore may be soft and more nasally when vibration occurs in the soft tissues of nasopharynx (the upper portion of the pharynx that connects the nasal cavity just above the soft palate) while vibration involving the uvula and soft palate may be louder and more guttural. For many habitual snorers, however, more than one area of the airways is usually involved, thus producing a variety of different snoring sounds in a single individual.

Snoring will typically reach peak intensity during the deepest stages of sleep (stage three or four) when the body is at its most relaxed. Sleep position also plays a role in snoring, adding to its volume. Habitual snorers with a preference for sleeping on their backs often snore the loudest because sleeping in a supine position (i.e. lying face upwards) narrows the airways more than other positions, enhancing the volume of the sound emitted.

In the medical field, the acoustics of snoring may be analysed and measured for a number of reasons, but this is generally done in order to distinguish normal snoring from snoring that may be indicative of a more serious sleep related breathing disorder (SRBD) such as upper airway resistance syndrome (UARS) or sleep apnoea syndrome (OSAS). ⁽⁵⁾

Snore analysis classifies sounds experienced during sleep in three ways:

• Snoring – ‘voiced non-silence’
• Breathing – ‘unvoiced non-silence’
• Silence

There are four energy sound types which are measured as a ‘snore map’:

• Type 1: A low-frequency single syllable snore.
• Type 2: Duplex sounds that have both low and middle frequencies.
• Type 3: Duplex sounds that have both low and high frequencies.
• Type 4: Triplex sounds that have low, middle and high frequencies.

Sound types can then be categorised according to two different snore patterns:

• Simple waveform snores: This pattern is normally characterised as a quasi-sinusoidal waveform with virtually no secondary internal oscillations (i.e. a range of variant sounds – a frequency range of 1 to 3 peaks - as a result of back and forth movement in a regular rhythm, mainly involving the tongue). This pattern normally has a high frequency due to tissue oscillation (i.e. vibration of the airway walls occurs around a neutral position) without actual closure of the airways being experienced.
• Complex waveform snores: This pattern usually involves a momentary closure of the airways as a result of ‘airway wall collision’. This pattern is characterised by equally-spaced, repetitive sounds (with multiple peaks) and is described as having a comb-like spectrum. Complex waveform snores are associated with palatal snores (loud vibrations involving the soft palate, uvula and back of the tongue result in airway closure).

Snoring frequency is measured in Hertz / Hz (the unit of frequency to measure, in this instance, the acoustic and mechanical vibrations of snoring). A small unit, 1 Hertz translates as one vibration cycle per second.

The frequency range of simple waveform snoring typically starts at 180 Hz and peaks at 300 Hz. The frequency range of complex waveform snoring typically begins at 60 to 130 Hz, with internal oscillations ranging up to 1 000 Hz.

The higher the frequency, the greater the obstruction of the upper airways. Lower frequencies produce a softer, more palatal obstruction sound. Mid-frequency snores indicate epiglottic involvement.

References:

^{2. Snoring and Obstructive Sleep Apnea, Third Edition. 2003. Snoring -  A general overview with historical perspectives: https://books.google.co.za/books?id=jUEFn5RfqqoC&pg=PA1&lpg=PA1&dq#v=onepage&q&f=false  [Accessed 21.02.2018]}

^{3. The Sleepyhead's Bedside Companion. Snoring: https://books.google.co.za/books?id=rhR2VjnDv6UC&pg=PT112&lpg=PT112&dq#v=onepage&q&f=false [Accessed 21.02.2018]}

^{4. Purdue University - Purdee e-Pubs. 18 July 2017. Biomechanics of Snoring and Sleep Apnea: https://docs.lib.purdue.edu/cgi/viewcontent.cgi?article=1008&context=bmewp [Accessed 21.02.2018]}

^{5. U.S. National Library of Medicine - National Institute of Health. January 1996. Snoring: analysis, measurement, clinical implications and applications: https://www.ncbi.nlm.nih.gov/pubmed/8834348 [Accessed 21.02.2018]}