Yes, humans were able to visualize sound waves long before the invention of the oscilloscope. The visualization of sound waves began to take place in the early 19th century with the development of a device called the "phonotrope" or "stroboscopic disc."
The phonotrope, invented by Joseph Plateau in 1832, consisted of a rotating disc with evenly spaced radial slits. When the disc was spun, a tuning fork or a musical instrument would be placed next to it, emitting sound waves. By adjusting the rotation speed of the disc, it was possible to create the illusion that the slits were stationary. When observing the rotating disc through a mirror or by looking at its reflection, the slits would appear as stationary lines. These lines visually represented the sound waves produced by the tuning fork or musical instrument.
The phonotrope was an early form of sound visualization, and although it did not provide a direct representation of sound waves as we know them today, it offered a way to observe the patterns and effects of sound in a visual manner. This early technique laid the foundation for further advancements in sound visualization.
Later in the 19th century, advancements in photography and the study of sound waves led to the development of more sophisticated methods for visualizing sound. For example, Édouard-Léon Scott de Martinville invented the "phonautograph" in 1857, which used a vibrating membrane to capture sound waves on a soot-covered cylinder. While the phonautograph was not designed for real-time visualization, it marked an important step in the recording and visualization of sound.
The invention of the oscilloscope in the 20th century revolutionized the visualization of sound waves. The oscilloscope allowed for real-time, accurate representation of sound waves as electrical signals, enabling scientists and engineers to study and analyze sound in great detail.
In summary, humans were able to visualize sound waves through various methods before the invention of the oscilloscope, starting with early devices like the phonotrope in the 19th century. These early techniques provided a visual representation of sound patterns and laid the groundwork for further advancements in sound visualization technology.