Overview⌗

Duration: ~30 minutes

Objective: Learn to use Adobe Audition’s essential tools for forensic audio examination: waveform view, spectrographic view, and critical listening techniques.

This lab provides hands-on practice with the concepts covered in the lecture on handling forensic audio evidence. You’ll learn to identify audio artifacts, analyze spectrograms, and understand the importance of working with proper file formats.

What to submit: Each exercise ends with a Turn in block telling you what to screenshot and what to answer. When you’re done, submit a folder of your screenshots and a single Word document (.docx) with your answers, organized by exercise number.

Screenshot tip: Capture the full Adobe Audition window so the file name, view mode, and any markers or zoom level are visible. Label each file with the exercise number (e.g., Ex2_artifact_at_3.4s.png).

Part 1: Installing Adobe Audition (5-10 minutes)⌗

Installation Steps⌗

Access Adobe Creative Cloud

  • Go to https://creativecloud.adobe.com/
  • Click “Sign In” in the top right corner
  • Select “Company or School Account”
  • Enter your school email address
  • Sign in with your institutional credentials

Install Adobe Audition

  • Once logged into Creative Cloud, find “Adobe Audition” in the list of apps
  • Click the “Install” button next to Adobe Audition
  • Wait for the download and installation to complete (this may take 5-10 minutes depending on your connection)
  • Launch Adobe Audition once installation is complete

Initial Setup

  • When you first launch Audition, it may ask you to choose a workspace
  • Select “Default” or “Edit Audio to Video” workspace
  • You can always change this later via Window > Workspace

Part 2: Download Lab Materials⌗

Download the following audio files and save them to a folder on your desktop called AudioForensicsLab:

Required Files⌗

If those links don’t work click here

Part 3: Adobe Audition Interface Overview (3 minutes)⌗

Opening Your First File⌗

  1. Launch Adobe Audition
  2. Go to File > Open (or press Ctrl+O)
  3. Navigate to your AudioForensicsLab folder
  4. Open forensic_speech_clean.wav

Understanding the Interface⌗

Adobe Audition has three main views for forensic work:

  • Waveform View (time domain) - Shows amplitude over time
  • Spectral Frequency Display (frequency domain) - Shows frequency content over time
  • Editor Panel - Where you’ll see your audio displayed

Key Interface Elements:

  • Top: Menu bar
  • Left: Files panel (shows open files)
  • Center: Main editor window (waveform or spectrogram)
  • Bottom: Selection/timeline information and transport controls (play, pause, stop)
  • Right: Properties and effects panels

Part 4: Waveform Analysis (7 minutes)⌗

Exercise 1: Basic Waveform Navigation⌗

With forensic_speech_clean.wav open, you should see the waveform display

  • Horizontal axis: Time
  • Vertical axis: Amplitude

Zoom Controls:

  • Horizontal zoom: Use the zoom slider at the bottom, or press = to zoom in, - to zoom out
  • Vertical zoom: Scrolling the mouse wheel
  • Fit to window: Press \ (backslash) to see the entire waveform

Practice Navigation:

  • Zoom in until you can see individual samples (dots with lines connecting them)
  • Zoom out to see the overall envelope of the audio

Audio Playback:

  • Press the Spacebar to play/pause
  • Click anywhere in the waveform to place the playhead
  • Press Home to return to the beginning

Turn in:

  • Screenshots: One zoomed in far enough to see individual samples; one zoomed out showing the full waveform envelope
  • Word doc questions:
    1. What does the vertical axis represent in waveform view, and what unit is it measured in?
    2. Describe what changed visually as you zoomed from the full envelope down to individual samples.

Exercise 2: Identifying Discontinuities⌗

Open forensic_with_artifacts.wav

Task: Find and identify audio artifacts

  • Look for abrupt changes in the waveform
  • Zoom in on suspicious areas
  • Click to place markers where you find artifacts

What to Look For:

  • Clicks: Sharp vertical spikes
  • Dropouts: Sudden drop to silence/zero amplitude
  • Discontinuities: Abrupt waveform changes that don’t match the surrounding audio
  • Edits: Unnatural transitions or cuts

Document Your Findings:

  • Write down the time locations (shown at bottom) where you find artifacts

Turn in:

  • Screenshots: At least two, each zoomed in on an artifact you found with the playhead or marker placed at its location
  • Word doc questions:
    1. How many artifacts did you find, and at what time positions (timestamps) are they located?
    2. Classify each artifact (click, dropout, discontinuity, or edit). Explain how the waveform shape told you which type it was.

Exercise 3: Critical Listening⌗

Open forensic_background_noise.wav

First Listen: Play through once focusing on the foreground (speech)

  • What is being said?
  • Is the speech clear and intelligible?

Second Listen: Play again focusing on the background

  • What background sounds can you identify?
  • Constant noise (HVAC, traffic)?
  • Intermittent sounds (doors, other voices)?

Practice Tip: Use good headphones if available

  • This reduces room noise and helps you hear subtle details
  • Keep volume at a moderate level to avoid ear fatigue

Turn in:

  • Screenshots: None required for this exercise
  • Word doc questions:
    1. Find a 30-second section with speech. What is being said? Transcribe as much as you can.
    2. Describe the background sounds you identified. Are they constant or intermittent? Give specific examples.

Part 5: Spectrographic Analysis (10 minutes)⌗

Exercise 4: Opening the Spectrogram View⌗

Open forensic_tones.wav

Switch to Spectral Frequency Display:

  • View > Spectral Frequency Display (or press Shift+D)
  • This shows the spectrogram

Understanding the Spectrogram:

  • Horizontal axis: Time (left to right)
  • Vertical axis: Frequency (Hz, low at bottom, high at top)
  • Color/Brightness: Signal energy (brighter = more energy)

Turn in:

  • Screenshot: forensic_tones.wav displayed in spectrogram view
  • Word doc questions:
    1. What do the three axes (horizontal, vertical, and color/brightness) represent in a spectrogram?

Exercise 5: Identifying Sounds in the Spectrogram⌗

With forensic_tones.wav displayed in spectrogram view:

Pure Tone:

  • Look for a horizontal line
  • This represents a single frequency sustained over time
  • Note the frequency (check the vertical axis)

Click/Impulse:

  • Look for a vertical line
  • This shows energy across all frequencies for a brief instant
  • This is characteristic of transient/impulsive sounds

Frequency Sweep:

  • Look for a diagonal line moving from low to high frequency
  • This shows how frequency changes over time

Turn in:

  • Screenshots: One for each of the three sound types (pure tone, click/impulse, frequency sweep). Annotate or label each one.
  • Word doc questions:
    1. At what frequency does the pure tone appear? How did you determine this?
    2. Explain why a click/impulse appears as a vertical line in the spectrogram.
    3. Describe the shape of the frequency sweep and the direction it moves.

Exercise 6: Time-Frequency Trade-off⌗

Adjust Spectrogram Settings:

  • Right-click in the spectrogram area
  • Select Settings > Spectral Displays…

Window Settings:

  • Try different FFT Size (also called block length):
    • Smaller FFT (e.g., 1024): Better time resolution, worse frequency resolution
    • Larger FFT (e.g., 8192): Better frequency resolution, worse time resolution

Observe the Differences:

  • With small FFT: Clicks are sharp/vertical, but tones are blurry/wide
  • With large FFT: Tones are sharp/horizontal, but clicks are blurred in time

Try Different Window Functions:

  • In the same settings, try different Window types: Hamming, Hann, Blackman-Harris
  • Notice subtle differences in how the spectrum appears
  • For most forensic work, Hamming or Hann windows are standard

Turn in:

  • Screenshots: One with a small FFT size (e.g., 1024); one with a large FFT size (e.g., 8192)
  • Word doc questions:
    1. How did the appearance of the clicks change between the small and large FFT sizes?
    2. How did the appearance of the tones change?
    3. In your own words, explain the time-frequency trade-off. Why can’t you get perfect resolution in both dimensions at the same time?

Exercise 7: Real-World Spectrogram Analysis⌗

Open forensic_background_noise.wav in spectrogram view

Analyze the frequency content:

  • Can you see the speech? (Usually appears as horizontal bands that change over time)
  • Can you identify background noise patterns?
    • HVAC hum: Often appears as horizontal lines at specific frequencies (60 Hz and harmonics)
    • Traffic: Broadband noise at lower frequencies
    • Other voices: Similar patterns to the main speech

Practice Zooming:

  • Zoom in on sections with interesting frequency content
  • Use the zoom tools to examine specific time ranges
  • Compare what you see to what you hear

Turn in:

  • Screenshot: forensic_background_noise.wav in spectrogram view, zoomed into a region where you can see both speech and background noise
  • Word doc questions:
    1. Describe how the speech appears in the spectrogram. What visual pattern does it form?
    2. Identify at least one background noise source visible in the spectrogram. At what frequencies does it appear, and is it constant or intermittent?

Part 6: Lossy vs. Lossless Formats (5 minutes)⌗

Exercise 8: Comparing WAV and MP3⌗

This exercise demonstrates why we never re-encode lossy formats in forensic work.

Open both files:

  • forensic_speech_clean.wav
  • forensic_speech_clean.mp3

Visual Comparison in Waveform:

  • Drag both into the files panel
  • Notice: They may look similar in waveform view
  • Small differences might be visible if you zoom in very close

Spectrogram Comparison:

  • View both files in spectrogram mode
  • Look at the high frequency content (above 8-10 kHz)
  • MP3 artifacts:
    • High frequencies may be completely missing (cutoff)
    • “Shimmer” or “swoosh” artifacts in the upper frequencies
    • Less sharp definition in transients

Listen Carefully:

  • Play short sections of each file
  • While the MP3 may sound similar, it has permanently lost information
  • This is why we never edit and re-save MP3 files in forensic work

Key Takeaway:

  • Always work with original, uncompressed files (WAV, AIFF)
  • If you receive MP3 files, convert to WAV first, work with the WAV, but preserve the original MP3
  • Never save edited audio back to MP3 format - this creates “generation loss”

Turn in:

  • Screenshots: One side-by-side or paired screenshot of the waveform view for both files; one of the spectrogram view for both files zoomed into the high-frequency region (above 8 kHz)
  • Word doc questions:
    1. What differences, if any, did you notice in the waveform view between the WAV and MP3 files?
    2. What did you observe in the high-frequency region of the spectrogram for the MP3 file? Describe any artifacts or missing content.
    3. Why is re-encoding an MP3 a problem in forensic audio work?

Part 7: Best Practices and Documentation⌗

Evidence Handling Protocol⌗

Even in this practice lab, get in the habit of proper forensic procedures:

Never Edit Originals:

  • In Audition: File > Save As and create a working copy
  • Always preserve the original file unchanged

Document Everything:

  • Create a text file or lab notebook
  • Note the time and location of any interesting findings
  • In real forensic work, include screenshots

Use Moderate Volume Levels:

  • Avoid the temptation to turn volume up very high
  • This can cause ear fatigue (acoustic reflex) and make you less sensitive
  • Take breaks if listening for extended periods

Systematic Approach:

  • Listen to the full recording first (overview)
  • Then analyze in detail (zoom in)
  • Alternate between visual (waveform/spectrogram) and aural analysis

Submission Checklist⌗

Use this checklist before you submit to make sure you have everything:

  • Exercise 1 — 2 screenshots (zoomed in, zoomed out) + 2 answers
  • Exercise 2 — 2+ screenshots (artifacts marked) + 2 answers
  • Exercise 3 — 2 answers (no screenshot)
  • Exercise 4 — 1 screenshot (spectrogram view) + 1 answer
  • Exercise 5 — 3 screenshots (tone, click, sweep) + 3 answers
  • Exercise 6 — 2 screenshots (small/large FFT) + 3 answers
  • Exercise 7 — 1 screenshot (speech + noise visible) + 2 answers
  • Exercise 8 — 2 screenshots (waveform + spectrogram comparison) + 3 answers

Troubleshooting⌗

Adobe Audition won’t launch?

  • Make sure you’re signed into Creative Cloud
  • Check that your school account is active
  • Try signing out and back in to Creative Cloud

Can’t see the spectrogram?

  • Make sure you’re in Waveform Editor (not Multitrack)
  • Press Shift+D to toggle spectral view
  • Check that a file is actually open

Audio playback issues?

  • Go to Adobe Audition 2026 > Settings > Audio Hardware
  • Make sure the correct audio device is selected
  • Check that your headphones/speakers are connected

Files won’t open?

  • Make sure files are in a supported format (WAV, MP3, AIFF)
  • Check that files aren’t corrupted
  • Try dragging the file directly into Audition’s interface

Additional Resources⌗

Questions? Bring them to the next class session or office hours.