Tiburon whistle 1

Chris Morrison & Roberto Velazquez
First version, June 13, 2002. Last version, December 23, 2003

In 2001, a stone whistle was found near the historic shoreline in Tiburon (See map), California U.S.A. by Chris Morrison, collector of rock minerals. Tiburon is a small town located 10 miles north of the Golden Gate Bridge in northern California (See postcard).

The discovery in words by Chris:

"The discovery was in an area 1 mile from an old Indian village by San Francisco Bay. This stone was out of its natural area by 20 miles so it was of interest to me to pick up. It was found in a construction ditch approximately 2 feet under the ground surface in a mixed clay and dirt composition. No other rocks or artifacts were found near the site, after intensive search. Milky quartz is not known in this locality. The stone shows extensive weathering such as seen in riverbeds or oceanside locations."

"I knew right away that it was a whistle (natural-geo-fact or man made?) I think it is natural as I have found natural quartz with cavities inside on the coast thirty miles away. But this one is unique... It has one cavity with two internal channels encased within the stone; a left and right one longer than the other. At the mouth of the whistle is a small clear quartz crystal tooth which is a natural part of the stone. The outside area of both sides to me shows signs of wear in the spots to be held when playing. Seeing that, I knew it was a whistle right away. I took it home and washed out what was sand in the chambers, put it to my mouth at the proper angle, as my Uncle (Prof. Arden Lanham is quite a collector and maker of clay whistles) had shown me on many of his. After a few minutes I hit a certain angle and there was the sound very much like your "wave example" (from the olmec ilmenite aerophone [1]) but much louder, enough to hurt ears close by and to be detected from afar."

Stone description and main dimensions (obtained by Chris).

The whistle is made up of a stone called milky quartz. It has a Mohs scale 7 out of 10. Surface of the stone is worn smooth with some areas having a slightly rougher texture than the rest. 15 small cleavage fractures are incorporated into the stone; 10 or so have the look as if someone had pressed a fingernail into clay (See figure).

It weighs 88 grms, measures 58mm by 45mm, varies from 15mm to 20mm in thickness with a 4mm hole which leads to the interior from one side. A 1 1/2mm by 2mm natural tooth of clear quartz is located near the 4mm opening (See figure). (Clear quartz tooth is visible in the background,see neg image in lower right for more detail). The right cavity measures straight in at 22 mm long and the left cavity measures 16mm long. Interior side measurements not available at this time but seem to be very narrow, maybe 5mm to 10mm (See figure). Water volume test to follow.

(See figure), showing small clear quartz geode found along the San Matao coast 30 miles south of Tiburon, in 2002. This is what I consider to be another geo-fact, which also can be used as a whistle but has a very weak output. The Tiburon whistle is a super charged race car compared to the Model "T" San Matao stone.

The interior cavity of the stone is shown with a x-ray, a detail enhanced (x-ray) and the interior dimensions (x-ray). The x-ray was taken from the side of the flashlight in the first picture. The x-ray shows that Tiburon whistle is an irregular Helmholtz resonator. But the sounding mechanism is very special, because the edge/edges (where the sound is generated) is/are inside the resonating cavity or cavities. The following remarks from Chris are very illustrative for the sounds generation:

"The last time I played it I almost thought I could get two tones out by shifting the airflow just slightly from left to right. I will work on that and try to get a recording of the results for you later. I was also just thinking how interesting that there is only one hole and that the sound is not made by blowing over the hole but going inside the chamber and that quartz tooth is the main driver of the sound, I have to aim my airflow almost vertical into the chamber to make sound. It takes sometimes a few minutes to get the angle JUST right to produce sound."

Field tests, sounds and dB measurements (by Chris).

Preliminary field tests show that the high pitch sound can easily be detected by the human ear at 350 meters. High compressed air 80psi and high human air flow produce an unbearable sound at close range to the unprotected ear. See Wav # 1, human moderate air and Wav # 2 compressed air 20psi. Using a sound level meter(we measured at a range setting of 100) we received a decibel reading of 98 at "A" weighting, and a 98 at "C" weighting at the 3 foot distance. Similar readings were achieved at a 2 foot distance (See figure).

Radiated acoustic power estimation and signal analysis (by Roberto).

The estimated radiated acoustic power 2 of 98 dB at 3 foot (1m) is equal to 0.08 Watts. In relation to musical instruments, it is equal than the the estimated radiated acoustic power of the piccolo (0.08 Watts). Tiburon whistle is louder than the olmec ilmenite aerophone [1], which is nearly 0.01 Watts, but there are similar perfectioned models that are louder like the "olmec" little face made of clay [1], which has a power of 0.315 Watts.

Spectrogram 1 shows the frequency components of the wav # 1 and spectrogram 2 is from the wav # 2. The pitch (F0) of those sounds are nearly 1477 Hz & 1615 Hz. The last one is higher due to the velocity of the input air flow and it has over tones. Tiburon whistle can be heard at a long distance, because its pitch is in the range of maximun sensitivity of humans (1 KHz - 4 KHz), like many ancient and modern whistles.

Works for the future

More investigation needs to be done on the possible past use and modification by humans. Microscope examination are planned along with a search for the original source location if possible.

Chris found the possible origin of the stone. He commented that " I plan to make another trip to look at the American River site above Auburn California, where I found the like samples of the Tiburon Whistle last year. After reviewing other areas I feel very confident that the Auburn site is the "possible" origin. The fact that the river leads to the San Francisco Bay also aids in my conclusion.


1. The main relevance of this short paper is that it is about the 1st known whistle consisting of milky quartz and it was discovered by contact through the Virtual Research Institute Tlapitzcalzin Web site. There are very few known aerophones made by nature like a stone whistle and a stone trumpet found in Ireland and some stone whistles from Japan.

2. The radiated acoustic power calculation was obtaided with the formulas 1 & 2 (in Excel format).

I = (10^-12)*10^(dB/10)          (1)

W = 4*PI()*I                              (2)

dB = Sound presure measurement in dB
I = Sound intensity (Watts/m2)
W = Radiated acoustic power (Watts)
PI() = 3.1416...


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