The bullroarer is one of the earliest-known devices for making sound, dating back at least 17,000 years to the Paleolithic period. Bullroarers are found the world over and seem to have been invented independently by many different cultures. They often have great ritual or religious significance and are strongly connected with male initiation rituals. In some societies bullroarers are taboo to women, who are not allowed to see or hear them.

WIKIPEDIA - BULLROARER

BULLROARERS IN ANTHROPLOGY

A simple bullroarer can be made by drilling a hole in one end of a wooden ruler and tying it to a 4ft length of string. When the bullroarer is whirled around on the string it spins rapidly and emits a whirring sound, together with a continuous tone that can be as low as 10 Hz. The spinning is produced by the bullroarer's shape - it is an airofoil (UK English) or airfoil (US English). A bullroarer usually has one flat side and one convex side. Most commonly made of wood, bullroarers can also be made of other materials such as bone. Although bullroarers may be as simply shaped as a ruler, a more usual shape is the lozenge or rhombus. Tear-drop or leaf shapes are also common.

Flint knives from the Neolithic and Bronze Age are found throughout Britain, often as ritual deposits. Many plano-convex knives are of a similar size and shape to bullroarers -with one flat side and one convex side, they tend to be vesica, rhombus or leaf-shaped.

Left: Two views of a typical plano-convex knife, knapped in flint.
Bronze Age/Beaker Period date, perhaps c. 2,000 - 1,500 BCE.

Taken from 'UK Finds Database' - FULL DESCRIPTION & DIMENSIONS FROM WEBSITE

Realising that the profile of this knife is an airofoil, and that the shape is one commonly used for bullroarers, I made a copy in quick-drying cement to experiment with. The cement was filed into shape, so more resembled a polished flint than a knapped one. The cement is not so dense as flint so I made the copy slightly larger to increase the weight and see how it whirled. A length of wire embedded in the cement was used to attach the string. It is assumed that a Neolithic craftsman would use string, rawhide and resin instead.

The replica plano-convex knife worked very well as a bullroarer. It was easy and satisfying to use, with a reasonably loud tone. I made another to roughly the same shape and size, then two more bar-shaped knives in different sizes. All were good bullroarers.

Next a bifacial knife was made, to the approximate size and shape of the first plano-convex knife. Both sides were rounded to the same profile. It was assumed that not being an airofoil section, it would produce no sound when whirled.

But instead, the bifacial knife made an even better bullroarer! It sounded much louder than the plano-convex version, with stronger bass frequencies.

The discovery that a bifacial knife can be a better bullroarer than a plano-convex knife was at first puzzling, but in fact airofoils do not have to be plano-convex.

WIKIPEDIA - AIROFOILS

Airofoils vary widely in shape and some are actually symmetrical, just as the bifacial knife. Even some aeroplane wings have airofoil sections that are almost symmetrical - particularly those designed for high-speed aerobatics rather then level flight.

To make a wooden bullroarer with a plano-convex airofoil is probably far easier than rounding both sides - this is certainly true when working in flint.
The first stage of knapping a flint knife is to break a suitably-shaped piece of flint from a core with a single blow, which can instantly produce an plano-convex profile.

There was still the question of how a string may be attached to an actual knapped flint. Lashed string or wet rawhide, shrink-tightened to fit, would be two methods possible with Neolithic technology.

Another way of attaching a string to a flint more securely would be to craft notches or projections onto the basic shape. There are many suitably-shaped flint knives in the archaeological record to make this a serious consideration.
This page from 'Windmill Hill and Avebury' shows a selection of flint knives found by Keiller on Avebury's West Kennet Avenue, some of which could be re-interpreted as having been shaped for tying to a string: WK AVENUE FLINTS

Some potential bullroarers may have already been classified as spokeshaves, bark-strippers, piercers or the rather vague 'fabricators'. The objects may well have been dual-purpose - both a useable tool and a bullroarer. There is evidence for dual-purpose objects in bullroarer cultures around the world.

Next, professional flint-knapper and ancient technology expert Karl Lee was consulted. Karl has spent many years perfecting his techniques for making useable and efficient flint tools: KARL LEE WEBSITE

Karl knapped a simple 10 cm long plano-convex knife in flint and found an elegant way of fixing the string using available Neolithic technology. He shaped a short piece of wood to one end of the flint and lashed it with fine string, after using a flint drill to make the string hole. The lashing was then covered with a mixture of beeswax and pine resin, resulting in a permanent and waterproof joint. Karl uses the same technique for fixing wooden handles to flint tools.

A string was attached and the flint knife was found to work well as a bullroarer. The bass frequencies are not very loud but this may be because they are subsonic (though this still has to be confirmed). This knife is bigger and heavier than any of the cement knives, so a lower pitch would be expected.

CONCLUSIONS:

These experiments were first reported, and the bullroarers demonstrated, at the 2nd meeting of the Acoustics and Music of British Music Prehistory Research Cluster at Durham University on 2/9/09. WEBSITE
A number of archaeologists and other specialists have also already expressed interest and support, but there is a great deal more work to be done.

The experiments has so far shown that plano-convex and bifacial flint knives certainly could have been used as bullroarers: whether they were or not is more difficult to prove.

Future plans include consulting more flint specialists, and studying some of the many knives in museum collections to see if they show any signs of having been lashed or adapted for connection to a string. More cement replicas will be made to the proportions of museum pieces, and tested as bullroarers. The pattern of deposition of flint knives around the country must also be studied. A detailed analysis of the tones produced by different knives will be made.

Considering the widespread use of bullroarers around the world, their use in prehistoric Britain would not be entirely unexpected, but there has so far been no evidence of their use. As bullroarers are most commonly made from wood or bone, any such examples would have been highly unlikely to survive anyway. It may be that wooden bullroarers were used in Britain and that the flint knives are symbolically similar; the connection may be entirely coincidental. Bullroarer cults are exclusively male and often enfore strict rules of secrecy; perhaps the knowledge that flint knives can produce sound was a secret known only to initiates? We'll never know, but the act of whirling a razor-sharp knife around on a thin piece of string is certainly very masculine...

This page will be updated as and when any more information becomes available.

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