Where do glaciers and icebergs get their beautiful blue color? This unique blue might be nature’s most brilliant, and the color arises in a very special way thanks to some surprising interactions between light and water molecules. Who knew physics could be so breathtaking? Continue reading
By Dan Quinn
A new variation on an old party trick: filling several wine glasses to different heights makes a “glass harp”, so submerging one empty glass in a basin of water is an “inverted glass harp”. It’s not the prettiest sounding instrument, but with enough practice, you could at least amuse your dinner guests. Continue reading
After sight, hearing is the most important of our five senses. Sound is caused by waves, and sounds are made by vibrating objects. Sounds can vary in two ways: amplitude and pitch. The amplitude of a wave tells us how much energy was used to produce it. The greater the amplitude, the greater the volume. Frequency is the number of waves or vibrations sent out in a specified amount of time; the faster something vibrates, the higher the pitch.
Question to the STAO Safety Committee
Can resonance rods do damage to a person’s hearing, especially if the demonstration is repeated several times during the day?
Tanya Malusev from Arbour Scientific measured the sound intensity. The maximum value achieved was 85 db. The frequency (not determined by them) occurs in a range of 2500 to 5000 Hz. OSHA indicates that habitual exposure to intensities can cause hearing damage. They published the following table:
8 hours at 90 db
4 hours at 95 db
2 hours at 100 db
0.5 hours at 110 db
The Canadian Centre for Occupational Health and Safety has also published a similar table listing sound intensity levels as they relate to hearing damage. As I interpret this, the resonance rods, while irritating (at this high frequency), will not do any damage to students/teachers at 85 db for such a short duration. This same interpretation was supported by Tanya (Arbour Scientific) in a personal email to me.
I hope that this information will be useful in making an informed decision as it relates to this particular demonstration. If new information is brought to your attention regarding this demonstration, I encourage you to share that with our committee. Please do not hesitate to contact us with further safety inquiries.
Click on the following link for a demo that illustrates the use of resonance rods
This engaging video gives us a detailed explanation of how we hear, the fundamentals of sound production, the overtone series, and how we distinguish one sound from another.