Sound

1. Gramophone

Mechanical table gramophone by HMV from around the 1920s, adapted for teaching by adding an electric pickup, allowing it to be connected to a loudspeaker. Originally, this model would have used a built-in horn. (ID: 4000.1.146)

2. Horn speaker

An acoustic amplifier used with gramophones and radios in the late 19th and early 20th century. (ID: 4000.1.538)

3. Horn speaker

An acoustic amplifier used with gramophones and radios in the late 19th and early 20th centuries. (ID: 4000.1.537)

4. Ruben’s tube

A demonstration device that visualises sound waves. Propane gas is fed into the tube from one end, and a speaker is placed at the other. When the gas is lit, the size of the flames reflects the amplitude of the sound waves. Invented by the German physicist Heinrich Rubens in 1905. (ID: 3000.29.10)

5. Helmholtz resonators

This set of resonators, named after 19th-century physicist Hermann von Helmholtz, demonstrates sound resonance in hollow chambers, similar to the tone heard when blowing across a bottle. Helmholtz resonators have been used to reduce unwanted frequencies and improve room acoustics. This set has been used in teaching at DTU since around 1900. (ID: 4000.1.1)

6. Wooden organ with experimental pipes

The pipes vary in material and size. Most resemble 19th-century experimental pipes by physicist and instrument maker Rudolph Koenig. Some are marked UT2–UT4 to indicate pitch, while others are built with glass fronts, cylindrical walls or with manometric capsules to visualise sound waves using flames. (ID: 4000.1.137)

7. Sound funnel

Used to emphasize the even overtones in the sound produced by an organ pipe. (ID: 4000.1.81)

8. Lissajous apparatus

Used to visualise two vibrations occurring at right angles. By showing patterns that reflect differences in frequency and timing, it helps analyse sound waves and other kinds of oscillations in acoustics, electronics, and mechanics. This instrument dates from before 1911. (ID: 4000.1.141)

9. Headphones

Manufacturer unknown, marking reads ‘Automatic København’. Likely mid-20th Century. (ID: 2018.3.41)

10. Random noise generator

An electrical circuit generates a random electrical signal (noise) that can be converted into sound waves. Produced by Bruel & Kjaer in 1963. (ID: 2019.9.49)

11. Electromagnetic tuning fork

An electric tuning fork designed to sustain its sound using a solenoid – a coil of wire that creates a magnetic field when electric current passes through it. Made by Max Kohl, circa 1900. (ID: 4000.1.176)

12. Tuning forks

Used to produce a precise musical pitch (pure tone) when struck. Invented in 1711, tuning forks became essential tools in acoustics and physics for studying sound waves and resonance. (ID: 4000.1.243)

13. Hartmann generator

Acoustic air-jet generator, invented by physicist DTU-professor Julius Hartmann in 1939. It is considered a major technological breakthrough, applied in technologies as diverse as fusion energy and microelectronics. (ID: 3000.91.60)

14. Sound survey meter

An instrument for measuring the intensity of sound in decibels (dB). From 1952. (ID: 3000.13.7)

15. Microphone

An early Bang & Olufsen model, likely from 1936. Carbon microphone housed in a pressed ‘Beolit’ casing (like Bakelite) and mounted in a ring to reduce vibration. (ID: 4000.1.217)