Beats Concept

Demonstrations in Beats

Two black metal vibraphone bars labeled A441 and A440, mounted vertically on a wooden base with orange felt pads at the nodes and red felt dampers on top, with a wooden mallet in front

Vibraphone Bars

Demonstrates acoustic beats — the periodic rise and fall of loudness when two nearly identical frequencies sound together. Two vibraphone bars tuned to 440 Hz and 441 Hz produce clearly …
Two aluminum rods mounted vertically in finger clamps on right-angle clamps attached to a bench clamp rod at a table edge, with a small hammer resting in the assembly

Singing Rod Beats

Two aluminum rods differing by 2 mm in length produce nearly identical tones that beat at ~3 Hz when struck simultaneously. Students hear the amplitude modulation directly and connect it …
Two glass whistles connected by brass fittings and wire, paired to produce slightly different frequencies

Quincke's Tubes

Two glass whistles with slightly different frequencies produce audible beats when blown simultaneously. Students hear the periodic amplitude modulation directly and can verify that by counting beats per second.
Agilent oscilloscope displaying two sinusoidal signals (blue and green) on channels 1 and 2, with their mathematical sum showing a beat pattern envelope below

Beat Patterns

Students observe acoustic beats both visually on an oscilloscope (using the math addition function) and audibly through a speaker. Demonstrates wave superposition and the relationship.