The L.F Hum in the room

In the 1980’s a number of residents of Bristol, enough to be called a cluster, brought to the attention of the media the phenomenon known as “The Bristol Hum”.

This was described by the complainants as comprising a low frequency noise or a dull drone although there were as many descriptions as the numbers of those reporting it. The common affliction had reached the status of having its own name after people on the bus, in the shopping malls or just out and about in the city compared notes and agreed on the form of the sound although in reality individuals attributed it to things in their own local areas including ventilation fans on a brewery building, cooling towers on an industrial site or the convergence of main roads and motorways through the Portishead corridor.

What was a constant amongst the Hum Believers was that the low frequency sounds were there all of the time, would not go away and made their lives miserable. The vast majority of Bristolians however appeared wholly oblivious of the torment of the minority.

Monitoring by Environmental Health, Sound Engineers and other Specialists could not detect anything that could be controlled by existing legislation with the conclusion that there was no such thing as the Bristol Hum.

This was no comfort to those who continued to lose sleep, have a disturbed night or feel a slight madness coming on. Drastic measures taken to try to beat the buzz included insulating under beds, re-orientating the position of the bed, going away for prolonged holidays, considering moving from the area and a few resorted to sleeping in their cars or garden sheds.

Here is the science bit.

The elusive hum is part of the Infrasound spectrum. This resonates at around 50 Hertz or cycles per second although in some studies frequencies have been as high as 80 Hertz and as low as 20 Hertz. What is clear is that the sounds are difficult to locate. In addition to conventional sound the low frequencies can also exert pressure on the human ear but in a wide and flat sound band there is no real difference in perception by either left or right aural sensors making the positioning and discerning unclear thereby adding to the confusion.

Audiologists have divided those sensitive to Infrasound into three groups. The first are those who have low frequency tinnitus often mistaking humming sounds as coming from external sources such as noisy neighbours. The second group have enhanced sensitivity to low frequency but for no apparent reason although stress and anxiety are cited as catalysts. The third group have an awareness of a specific low frequency signal, not necessarily intense but enough to cause a nuisance.

 In less enlightened times in history those insistent on describing noises not detectable by others were at risk of being locked up or burnt at the stake. We may feel that we have the trappings of a more civilised, rational and tolerant society but there is still little sympathy and understanding of the suffering of the minority by those who should be administering some relief through medicine, counselling and therapy.

There are some signs of a slow improvement in the attitude of the caring sector towards Infrasound sensitivity but if the hum does not fall within the guidelines and parameters of Environmental Health and other Statutory Powers on noise and anti-social behaviour then very little can be done.

Infrasound is a powerful source.

The eruption of Krakatoa sent low frequency sounds on five circumnavigations of the earth. In the man made world the sounds of Concorde in full supersonic mode were detected over a 7000 miles distance.

We should not forget the purpose of the human sense of sound. Whilst it is taken for granted as a means of listening to music, communicating and media immersion it’s prime purpose in evolving Man was as an audio early warning system. Any unrecognisable or strange sounds still activate the fight or flight electrical signals in the brain although in modern life we are overwhelmed by noise from every quarter. Everyday life exposes us to low frequency emissions from power lines, underground trains, electricity transformers, industrial processes and traffic amongst many others.

The source of that annoying and disturbing hum and therefore something to blame for it is, however, as elusive as ever. 

If we cannot identify a cause for a specific problem then it tends to assume a magical, mystical and unworldly quality and we can hide behind such things as an explanation even if it is not a satisfactory one.  

Auckland in New Zealand had an outbreak of headaches and nausea attributable to a Hum Hotspot in recent years and scientists claimed to have isolated and recorded the offending sound. When broadcast via the internet those reporting feeling ill agreed almost unanimously that the low frequency drone was the one that had been heard. No specific source was ever attributed.

Conspiracy Theorists have sought an explanation of the phenomena through the use of Infrasound by the military as a weapon. Experimental research in the Cold War Years was indeed carried out but abandoned as it was not possible to adequately contain, concentrate and deploy a low freqiuency signal against an enemy and the risks of collateral damage were too high. There have been considered applications in crowd control in that a burst of sound can cause vomiting and diarrhoea but the potential contravention of Human Rights and common decency towards another human being fortunately still prevail.

There is a growing consensus amongst those who have studied the Infrasound subject that it may be individuals who are sensitised in a similar way to those with specific allergic reactions to certain substances. Therapies to deal with sensitivity to the hum have been based on trying to re-tune the brain using relaxation techniques and digitalised sounds of rainfall, rivers and oceans have been successful in screening out the low frequency annoyances.

One documented case study emphasises the ongoing difficulty in pinpointing any one specific cause. A continuous hum was a distraction to a resident of Chelmsford, Essex who had recently moved back to the UK after many years abroad. He had had no previous problems but this particular noise was a distraction every night causing loss of sleep and anxiety. The man took to wandering around the local area after dark trying to find the source with candidates being a grain dryer, power transformers and ventilation fans at a nearby Golf Club. None of his family and friends were aware of any sound annoyances. After 12 months it was a case of moving away to another area, this time some distance away in the Midlands. The new residence in a town was intended to introduce a general level of background noise in an attempt to screen out the hum. Agonisingly the same noise was present although with subtle differences. He was still awoken at 2am but now with the unwelcome side affects of teeth chattering and whole body resonance. Monitoring through conventional sources drew a blank. The Midlands residence was a newer property than that occupied in Chelmsford and the hum victim began to research modern construction methods and materials as a probable cause.

There may be some justification in this line of enquiry given the interaction between components in a typical house from the cavity wall to internal plasterboard, stud work and scope for resonance and vibration. The unfortunate man is now on the move again and is looking to carry on his experiment in a stone walled and thatched house next. If that fails to explain the suffering and torment then there are proposals to travel overseas again, stand on a mountainside, in the desert, on an ice-cap and on an island to try to make sense of the whole thing.