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Background Information

Sim name: Wave on a String

Link: http://phet.colorado.edu/en/simulation/wave-on-a-string

Goal: Analyze the sim and brainstorm design issues (including accessibility and inclusion design issues) and possible solutions. This sim is not currently a sim being worked on as part of any grants - it's purely chosen as an example for a design exercise.

In attendance:

  • Dana Ayotte
  • Simon Bates
  • Julia Foster
  • Jesse Greenburg
  • Alan Harnum
  • Jonathan Hung
  • Justin Obara
  • Tim Park
  • Sepideh Shahi
  • Taliesin Smith
  • Godfrey Wong

This document is a compilation of notes resulting from a meeting that occurred on July 21, 2016

Description of Sim:

Link to the sim: http://phet.colorado.edu/en/simulation/wave-on-a-string

  • On first load, the screen shows a string of beads attached to a wrench on the left side and attached / anchored to a clamp on the right side.

  • The wrench can be moved up and down with the mouse which causes a wave to travel across the string to the opposite end. The wave will rebound back.

  • Other controls on the sim modify the behaviour of the wave - “damping” and “tension”.

  • You can change the right anchoring to be “fixed”, “loose” and “no end”

  • You can also change the wrench control scheme from “manual”, oscillate, and pulse.

Some Challenges

  • Wrench control

    • Range - controls amplitude

    • Speed of movement - controls frequency / period of waves

  • Perception of string movement

  • State of the sim as a result of user actions

Wrench control challenge

  • The wrench controls two variables:

    • Amplitude

    • Frequency

  • What would this look like as native HTML controls for keyboard and screen reader access?

    • Amplitude could be a range slider and the speed of which the slider is moved controls the frequency.

    • Raises concerns for motor control

    • Could add an accelerator key of some sort which speeds up movement on the slider.

    • Inequality in experiences: Even if you use a slider or an accelerator key, the end user experience is far from the visceral experience that someone using a mouse has.

  • Could also consider having the pointer directly manipulate the wrench without having to click / depress buttons.

    • This would imply having the user switch into a special mode where the mouse / tracker acts as a wrench (i.e. shaking it would shake the wrench).

    • But the user would get into states where their mouse is controlling the wrench and not the actual cursor on the screen which could be very confusing.

    • It’s also possible to use the GPII Nexus to have another device control the wrench (a proof-of-concept was made on July 22nd using the tilt sensors on an iPad Mini to control the wrench).

    • Some users can not physically use a mouse or hold another device. How would control be done in this case?

      • Head tracker was mentioned but this could interfere with viewing and focussing on the wave

Perception of String Movement

  • Initial thought - map the wave created by the string directly to sound as a way of sonifying the data. But there are some issues:

    • How would you sonify the situation where the wave bounces back from the end point?

    • It’s possible to have a complicated scenario where the user reduces the tension and damping to 0, and create multiple waves. The waves are constantly colliding and passing through each other - what would this even sound like?

      • The sound of the waves still have to sound nice (even when multiple waves collide)

    • What would the sound differences be for fixed, loose, and open ended?

    • Using volume, pitch to represent amplitude and repetition to represent frequency was suggested

  • Is it useful to sonify a single fixed point on the string?

  • How can haptics be used?

    • Something like a braille device where you can feel the waves.

  • What are the most necessary pieces of information that need to be perceived? (what is the main objective of the physics sim? Understanding concepts or completing calculations?)

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