AI is appropriate for teaching undergraduate students in Speech and Hearing Science, Audiology, Communication Disorders, and Experimental Psychology. Graduate students in those disciplines, as well as students of biomedical, electrical, and acoustical engineering, will also find the material stimulating and educational. AI can be used either by instructors for classroom demonstrations or by students themselves for direct experimentation.

AI contains major units on

  • Signals and Signal Transformations
  • Physical Acoustics of Hearing
  • Monaural Perception of Stationary Signals
  • Monaural Temporal Phenomena
  • Binaural Hearing
  • Spatial Hearing
  • Pattern Perception

Within each unit are lessons on specific topics. Many of the lessons allow the student to set up an experiment and collect data. Others present interactive demonstrations. Each lesson is accompanied by a Background section providing an introduction to the topic, and an Instructions section that describes how the interactivity is used.

The development of AI was carried out with support from the National Institute on Deafness and Other Communication Disorders.

Hardware Requirements

  • Intel Pentium (or equivalent) CPU
  • Windows® XP/Vista/7/8
  • 1024 x 768 (or higher) resolution monitor


Q.  Does Auditory Interactivities run on Windows 8/7/Vista/XP?

A. Yes.

Q.  I get errors while trying to install/run Auditory Interactivities.

A. On operating systems based on NT 5 (Windows® 2000, Windows® XP, Windows® Vista, Windows® 7, Windows® 8) it is necessary to log in as an administrator to properly install Auditory Interactivities. While installing as a Power User may appear to succeed, in fact the program will not be correctly installed. Note: On Windows® XP all user accounts other than Limited Users normally have administrator privileges and may be used to install Auditory Interactivities.

Q.  How can I enlarge the AI window?

A.  Please see the section entitled “Screen Area” on page 7 of the AI User Guide.

Q.  How should I set up my audio system?

A.  Please see the section entitled “Audio Setup and Calibration” starting on page 8 of the AI User Guide.

Q.  How can I see the Background and Instructions at the same time as the main interactivity window?

A.  The Background and Instructions for all of the lessons are available in a file called Background and Instructions.pdf on the AI product CD-ROM. Click on that file to bring up Adobe Reader. Navigate to the Background or Instructions for the specific lessons you want. If you do not have Adobe Reader installed on your computer, it may be downloaded free from the Adobe website at adobe.com.

Q.  What should I do if the audio becomes corrupted?

A.  Exit from AI and re-start. If that does not fix the problem, try re-booting your system.

Q.  Some objects on the screen obscure other objects.

A.  Make sure that you have selected the Windows Font Size properly. See page 6 of the AI User Guide for instructions on this setting.



Interactivity is the hallmark of AI. The high degree of interactivity can be illustrated using the lesson on tone detection in noise as an example. This particular interactivity was designed to teach about the concept of the auditory critical band. It does so by allowing the students themselves to replicate the psychoacoustic studies that were originally performed to document the frequency-analysis capabilities of the ear.

AI Interactivity

The main screen shown here gives the student control of the signal-generation parameters relevant to this experiment through the sliders associated with each piece of equipment in the block diagram. A sine oscillator generates a continuous sine wave; the two sliders under the oscillator allow variation in the frequency and the amplitude of the sine signal, current values of which are displayed to the right of the sliders. The sine signal passes through a switch that controls the on-time, the interstimulus interval (ISI) and the rise/fall (R/F) of the pulsing signal. The masking noise is created by the noise generator, whose amplitude parameter is controlled. The noise is bandpass filtered through a filter whose center frequency and bandwidth are controllable. The out put of this filter is measured by the level meter and is then mixed with the signal. The sum of signal and noise are monitored for clipping and delivered to one-channel of the computer’s audio output device. The graphic icon suggests that earphones should be used for listening.

This setup will generate a tone signal pulsing on and off continually against a bandpass noise background. For any set of stimulus parameters a listener can adjust the signal’s level so that the signal is at detection threshold. If this measurement is made as the noise bandwidth is varied, the results should describe the classic critical bandwidth finding.

Data Collection And Storage

AI Data Collection

In approximately half of the lessons in AI it is possible to record measurements. In many of these the program provides tools for saving, displaying and exporting collected data to a file. When the “record settings” buttons at the bottom of an interactivity screen is clicked, the current settings of the parameters are stored in a results buffer. The “store data in file” button will export all collected data in the session to a text file for easy access by other data analysis or plotting programs. The “clear results” button clears the data buffer in preparation for a new session.
In addition to these tools, AI also provides a plot of recorded data, accessed by the “show plot” button. Clicking that button brings up a plot of the results of the adjustments of signal level at different bandwidths, like that shown here. The panel on the left plots the signal level at threshold against the noise bandwidth. The panel on the right displays a table containing all of the parameters in effect for each click of the “record settings” button. Having all of the data saved in a table like this means that one can conduct an experiment using any pair of parameters as the independent and dependent variables.

Background And Instructions

AI Instructions

Each lesson is accompanied by a text explanation that gives a basic introduction to the phenomenon under study. These are intended to supplement, not supplant, a textbook and instructor.

The use of each lesson and how it is controlled is given in clearly detailed Instructions. The initial part of the Instructions for the Critical Band lesson is shown here.


Unit 1: Signals And Signal Transformations

Lesson 1. Sine Waves

  • Interactivity 1. One Sine Wave
  • Interactivity 2. Two Sine Waves
  • Interactivity 3. Vectors

Lesson 2. Fourier Analysis And Synthesis

  • Interactivity 1. Periodic Signals
  • Interactivity 2. Aperiodic Signals

Lesson 3: Windows And Filters

  • Interactivity 1. Time-Domain Windowing
  • Interactivity 2. Frequency-Domain Filtering

Lesson 4. Nonlinearities

  • Interactivity 1. Distortion

Unit 2. Physical Acoustics Of Hearing

Lesson 1. From Sound Field To Eardrum

  • Interactivity 1. Diffraction Of Sound By A Sphere
  • Interactivity 2. Sound Propagation In The Ear Canal

Unit 3. Monaural Perception Of Stationary Signals

Lesson 1. The Range Of Hearing

  • Interactivity 1. Threshold Of Hearing

Lesson 2. Loudness Of Pure Tones

  • Interactivity 1. Finding A Scale Of Loudness
  • Interactivity 2. Loudness Recruitment Of A Tone In Noise

Lesson 3. Just-Noticeable Differences In Frequency And Intensity Of A Tone

  • Interactivity 1. Jnds In Frequency
  • Interactivity 2. Jnds In Intensity

Lesson 4. Pitch Of Complex Sounds

  • Interactivity 1. Pitch Of Harmonic Complexes
  • Interactivity 2. Pitch Of Inharmonic Complexes
  • Interactivity 3. Circular Pitch

Lesson 5. Simultaneous Masking

  • Interactivity 1. Tone-In-Noise Detection And The Critical Band
  • Interactivity 2. Tone-On-Tone Masking: Masking Patterns
  • Interactivity 3. Tone-On-Tone Masking: Psychophysical Tuning Curves

Lesson 6. Timbre

  • Interactivity 1. Timbre Differences In Steady-State Sounds
  • Interactivity 2. Spectral-Shape Discrimination
  • Interactivity 3. Monaural Diplacusis

Lesson 7. Auditory Nonlinearity And Afterimages

  • Interactivity 1. Searching For 2f1-F2
  • Interactivity 2. Zwicker Tones

Unit 4. Monaural Temporal Phenomena

Lesson 1. Temporal Resolution

  • Interactivity 1. The Modulation Transfer Function
  • Interactivity 2. Duration Discrimination

Lesson 2. Temporal Integration

  • Interactivity 1. Detection As A Function Of Duration

Lesson 3: Non-Simultaneous Masking

  • Interactivity 1. Backward Masking
  • Interactivity 2. Forward Masking
  • Interactivity 3. Pulsation Threshold: Psychophysical Tuning Curves

Unit 5. Binaural Hearing

Lesson 1. Lateralization

  • Interactivity 1. Effects Of Interaural Differences On Intracranial Image Position
  • Interactivity 2. Jnds In Interaural Time
  • Interactivity 3. Jnds In Interaural Level
  • Interactivity 4. Binaural Beats
  • Interactivity 5. The Precedence Effect

Lesson 2. Detection

  • Interactivity 1. Masking Level Differences

Lesson 3. Pitch

  • Interactivity 1. Huggins Pitch

Unit 6. Spatial Hearing

Lesson 1. Simulating Anechoic Listening

  • Interactivity 1. Sources In The Horizontal Plane
  • Interactivity 2. Sources In The Median Plane
  • Interactivity 3. Tone Detection In Noise
  • Interactivity 4. Speech Reception In Noise

Lesson 2. Phantom Images

  • Interactivity 1. Intensity-Difference Stereophony (Panning)
  • Interactivity 2. Delay-Difference Stereophony (The Precedence Effect)
  • Interactivity 3. Franssen’s Illusion

Lesson 3. Echoes

  • Interactivity 1. Sound Quality With A Single Echo
  • Interactivity 2. The Haas Effect

Lesson 4. Simulating Reverberant Listening

  • Interactivity 1. Sources In The Horizontal Plane
  • Interactivity 2. Binaural Squelch

Unit 7. Pattern Perception

Lesson 1. Temporal Order

  • Interactivity 1. Temporal Order Identification
  • Interactivity 2. Time-Reversed Sounds

Lesson 2. Streaming

  • Interactivity 1. Streaming By Pitch
  • Interactivity 2. Streaming By Location
  • Interactivity 3. Locating Clicks In Speech

Lesson 3. Source Segregation

  • Interactivity 1. Four Cues For Segregation

Lesson 4. Continuity

  • Interactivity 1. Tones And Noises
  • Interactivity 2. Picket-Fence Effect With Speech


Please consult the following documents for important information about Auditory Interactivities:


AI User GuideAI User Guide (PDF)