The US Actually Funded Research For This Effect
The Action Lab
6 min, 13 sec
The video explains the 'hot chocolate effect,' a phenomenon where tapping a mug of hot chocolate results in the pitch of the sound increasing over time.
Summary
- The 'hot chocolate effect' was discovered by Professor Frank Crawford in 1974 when tapping a mug of hot chocolate led to a noticeable increase in pitch over time.
- The effect can be replicated with hot water from the tap, which initially contains many dissolved air bubbles that are released, affecting the pitch.
- The pitch of the tapping sound is correlated with the number of air bubbles present; more bubbles result in a lower pitch, and fewer bubbles result in a higher pitch.
- The speed of sound in the water and the height of the water in the mug determine the pitch, which is dependent on the density and compressibility of the medium.
- The video includes a promotion for Hensen Shaving, a company offering precision CNC machined razors.
Chapter 1
The video begins by introducing the 'hot chocolate effect,' a phenomenon where the pitch of a sound increases while tapping a mug of hot chocolate.
- The video's host mentions that most people might not notice the effect unless they tap their mug while drinking hot chocolate.
- The increase in pitch is termed 'the hot chocolate effect' and was documented in scientific literature in 1980.
Chapter 2
The discovery of the hot chocolate effect and subsequent research by Professor Frank Crawford are discussed.
- Professor Frank Crawford from the physics department of Berkeley discovered the effect in 1974 with his friend Nancy Steiner.
- Crawford found that the effect is not unique to hot chocolate and can be replicated with hot tap water.
Chapter 3
The video explains the effect using hot tap water and how it relates to the presence of air bubbles.
- Hot tap water becomes cloudy due to dissolved air, which forms bubbles as the water cools and pressure decreases.
- The pitch of the tapping sound corresponds with the amount of air bubbles; as bubbles rise, the pitch increases.
Chapter 4
A correlation is established between the number of bubbles in the water and the pitch of the sound.
- More air bubbles in the water lead to a lower pitch, while fewer bubbles result in a higher pitch.
- The reverse hot chocolate effect can be observed with tap water, where the pitch decreases initially as air comes out of solution and then increases.
Chapter 5
The video delves into the concepts of sound and how the speed of sound in different media affects the pitch.
- The speed of sound is faster in water than in air, but changing the speed of sound doesn't always alter the pitch, as demonstrated with a tuning fork.
- To change the pitch, you must alter the natural frequency, which is possible by changing the density of the medium, affecting the speed of sound.
Chapter 6
The phenomenon is further explained by examining standing waves and the speed of sound within the mug.
- The sound from tapping the mug comes from the standing waves created by the speed of sound in the water and the mug's height.
- The speed of sound in a fluid with air bubbles is lower, which results in a lower frequency and lower pitch sound.
Chapter 7
The video includes a sponsored segment promoting Hensen Shaving's precision razors.
- Hensen Shaving, known for aerospace engineering, offers precisely machined razors.
- Their razors hold the blade at a 30-degree angle, promising a close shave with no irritation and built to last a lifetime.
- A special offer is provided to the viewers to try the Hensen al13 razor.
Chapter 8
The video concludes with an explanation of why the hot chocolate effect happens in both hot chocolate and hot tap water.
- The hot chocolate effect in actual hot chocolate is due to the introduction of air bubbles by the chocolate powder.
- Stirring the hot chocolate reintroduces air bubbles, making the phenomenon repeatable.
