Speaker and Baffle - Physics Demonstrations - Speaker and Baffle | Physics Undergraduate Labs

Purpose

An oscillating speaker cone emits sound from both front and back surfaces, 180° out of phase. Without a baffle, these waves interfere destructively ("acoustic short-circuiting"). Inserting the speaker into a baffle makes the tone dramatically louder and clearer, demonstrating the wave nature of sound and why speakers need enclosures.

Large plywood baffle board with circular hole in center; small speaker on ring stand at left, function generator on bench below

Close-up of small speaker driver seated in the plywood baffle hole, showing dark cone with two-blade center piece

Figure 1: Setup: speaker on ring stand (left), plywood baffle with mounting hole (center), and function generator (bottom right). The speaker slides into the baffle hole for comparison.

Figure 2: Speaker driver seated in the baffle hole. The baffle separates front and back sound waves, preventing destructive interference.