ICONISMUS II. illustration: A full-page scientific engraving illustrating the acoustics of a speaking trumpet or tuba stentorophonica. At the top of the frame, a human head is shown in profile, blowing into the mouthpiece of a long, flared conical instrument labeled "A".

The diagram depicts the propagation of sound waves using a series of concentric circles and intersecting lines. The interior of the trumpet is marked with a vertical sequence of Latin and Greek characters on both the left and right sides of the central axis: V, μ, T, λ, S, κ, R, φ, Q, η, P, ψ, O, ε, N, δ, M, γ, L.
The sound waves emerge from the bell of the trumpet (marked with points B, K, C, D) and expand outward in large concentric circles that fill the lower two-thirds of the page. Several focal points of wave interference or secondary propagation are labeled with capital letters: H and I on the upper sides, E and F on the lower sides, and G at the very bottom center. The central path of the sound is depicted as a series of overlapping elliptical wave fronts expanding from the mouth of the instrument.