Importance of Waves in STEM Career Preparedness

From quantum physics to gravitation, from the micro to the macro scale, waves are pervasive in the physical world. A deep knowledge of the behavior of waves is not only fundamental to the physical sciences, but is also necessary for understanding diverse concepts in many fields such as chemistry, neurobiology, or geology, electronic and structural engineering. Moreover, understanding waves is a key element of understanding signal processing and is thus an important component of career preparedness for the information and communications technology (ICT) workplace and the entertainment industry. Listening to Waves seeks to build a connection between a physical phenomenon that is ubiquitous in our everyday lives (sound), the physics behind this phenomenon (waves), and applications of this knowledge that might be conducive to careers in STEM.

Course Description

The classes will be primarily taught by computational neurobiologist Dr. Victor Minces and by cognitive scientist and ethnomusicologist Dr. Alexander Khalil. Through participation in this program students will learn the hidden and ubiquitous world of waves as they make and analyze musical sound. To accomplish this they will create waves and vibrations in physical objects (building their own unconventional instruments), use computers to analyze their waveforms and acoustic properties, and explore how sound is propagated through the environment and represented in the brain. In addition to the activities carried out with the instructors, we will engage adult volunteers from academia and industry who specialize in extended use of wave theory to explain the role of waves in their respective fields, thereby emphasizing the linkage between STEM domains. This will further promote STEM and ICT career awareness using waves, a subject the students already have experience with, as a common denominator. The lesson plan (see below) is designed as a series of experimental activities that stimulate critical thinking to integrate creativity with signal analysis technology. At the end of this program the participants will create experimental musical instruments that will be presented as installations in a public art-science-show. In this way the understanding of waves through sound will extend beyond the participants to their broader communities.

Learning Goals

The learning goal is for students to understand what sound is, how objects vibrate, and how sound is propagated in space. We intend for students to develop intuitive notions of frequency decompositions (Fourier transforms). By the end of this program the participants should be able to connect a sound they hear, the characteristics of the object that created it, its waveform, and its spectrogram; and they should understand that the wave knowledge they acquired applies to various domains other than sound.

Lecture topics

Making sound, watching sound- We will introduce the microphone as a tool to measure oscillations either in air pressure or (as in contact microphones) in physical objects. Equipped with both free-field and contact microphones, participants will roam the environment (school) recording sounds and creating sounds by knocking on objects and using their voices We will bring some interesting-sounding objects, including musical instruments, to the class for them to measure. Participants will hear the recordings while visualizing the sounds on Audacity, a free and open source audio-editor program. In guided discussion they will elaborate on the relationship between the perceptions - such as loudness, duration, or pitch - and the visually presented waveforms associated with them. We will use tuning forks to introduce the concept of a pure sine wave and the association between pitch and the frequency of the sine wave. The participants will use free software, Audacity, to measure the number of oscillations per unit time and compare it to their auditory perception. Frequencies will be related to musical tones. We will let them explore spectrograms, generated by audacity, and discuss how the peaks depend on the frequency presented, we will not explain the mathematics of Fourier transforms but rather let them explore spectrograms as an object to be understood. Participants will be allowed to take the microphones and sound recorders home and explore the sonic world around them, bringing recordings they find interesting into the class for sharing and analysis, this activity will continue throughout the program. As the sounds that can be recorded through the contact microphones are not regularly available to us in everyday life (we can’t hear them), having these microphones will allow them to explore a whole new world of sound.

Making waves- Students will use slinky toys (metal coils) to understand how waves are propagated. They will send pulses through the slinky and evaluate qualitatively how the speed of propagation depends on the tension, measured as number of coils per inch and the deflection of the slinky when a weight is added to it. They will exert force on the slinkies in an oscillatory fashion at different frequencies to understand standing waves and resonances. They will compare the resonant frequencies and node location of the different harmonics, and evaluate how resonant frequencies vary with the tension and the length of the slinky. They will discuss how the movement they observe relates to the waveforms observed in the previous section.

Good vibrations- Participants will experiment with vibrations in objects. Building on their newly acquired knowledge of slinky vibration they will start with strings and compare the sounds (their physical perception and wave signatures measured with the oscilloscope), evaluating how the sound depends on length and tension. They will use big objects, such as long rods, so they can see how they vibrate, they will tap the objects and find nodes. They will use the same materials but with shorter lengths to appreciate how vibrations become invisibly small while at the same time becoming audible. We will use a stroboscopic light to observe how an object “freezes” when it is in synch with the frequency of the light and thus visualize the frequencies of vibration. Students will analyze the vibration of two dimensional objects (like gongs), use chalk powder to find the nodes and mount the objects on those nodes. They will analyze the frequencies in strings, gongs and drums, and discuss how they vary with shape, thickness, and tension. They will see how the sound changes when they “force” a node by fixating the objects on a certain point.

Sympathetic vibrations and the cochlea - Now that students understand how different objects vibrate and resonate, and how sound is transmitted through the air, they will experiment with sympathetic vibration. This will involve playing instruments and singing into string instruments and measuring how the different strings vibrate and how the resulting resonances depend on an instrument’s tuning. Using many strings of different sizes and tensions, attached to contact microphones, they will build an “artificial cochlea”, projecting simple and complex sounds into it and analyzing the vibration profile. This will help them to understand how sound is processed in the early stages of the brain. It will also allow them to understand how complex sounds can be analyzed in terms of the individual frequencies (frequency decomposition).

Hidden sounds - We will have a field trip to the street and the park. We will carry “stethoscopes” and explore the sounds of the objects around us. Trees, light posts, fences, manholes, etc. The sounds will be explored on site and carried to the class room to analyze their modulations and frequency content. This will serve to provide understanding that sound waves are ubiquitous and not restricted to voice and musical instruments. It will also provide a model to analyze the different aspects of sound.

Creating instruments - Equipped with all the knowledge gathered in the previous sections the students will create experimental musical instruments. They will use different resonant boxes, strings, patches, two dimensional objects such as wood and sheets of metal, rubber bands, pipes, rods, bubbles, water, contact microphones and amplifiers, frequency transducers, etc. These instruments may not produce conventional music at all but rather produce or manipulate sound in ways students have learned in previous modules.

Other waves - In parallel with the instrument-making activities, we will host guest lecturers from the physics department at UCSD, the Scripps Institution of Oceanography, and industry (i.e. Qualcomm) to explain what role waves play in their work and what other types of waves are (gravitational, quantum mechanical, electromagnetic for communication and light, water waves). Using two-pin-hole diffraction and lasers, we will demonstrate wave-like properties in light. We will explain how radios work. This is intended for participants to understand just how pervasive the wave phenomenon is.

Exposition -The participants will present their instruments individually in a show, explaining how they built them and how they work (how they vibrate). Each instrument will have an associated real time visualization of the frequency content. The instruments can remain as a permanent “sound installation” in a museum or library.