11-03-25 Pitch & Concepts in Psychoacoustics

Transition from Physics to Other Scientific Concepts

• Last week of physics course discussed.

• Future discussions will involve heating, anatomy, and fusion.

• Connections to previously learned concepts will be emphasized in the upcoming weeks.

Fundamental Concepts of Sound

Pitch

• Definition: Pitch is a psychological correlate of frequency.

• High-frequency sounds have a high pitch (e.g., soprano voice) and low-frequency sounds have a low pitch (e.g., bass voice).

• Parameters of Sound: Important attributes of sound include:

  • Pitch

  • Loudness

  • Quality

• Examples:

  • Describing sounds based on pitch (e.g., low pitch vs high pitch).

  • Smallest pitch difference detectable in normal individuals can range from 3 Hz to 5 Hz.

Doppler Effect

• Explanation: When a sound source moves away, the pitch decreases; when it approaches, the pitch increases.

• Real-life example: The sound of an ambulance passing by.

Measurement of Sound Frequency

Human Perception of Frequency

• Humans cannot accurately identify the frequency of a sound (

• Example response might be "I think my pitch is lower" rather than providing an exact frequency in Hertz.

• Frequencies are measured in Hertz (Hz).

Perceptual Comparison of Sound

• Ability to compare pitch is relative:

  • Example: "The pitch of sound A is twice that of sound B."

  • Instruction from conductors to singers often refers to intervals (e.g., two tones higher).

Historical Development of Pitch Measurement

• Researchers created a scale for measuring pitch by presenting a reference tone and asking participants to identify pitches that are higher or lower.

• Data collected from various individuals led to the establishment of normative data for pitch perception.

Complex Periodic Sounds

Pitch and Frequency in Complex Sounds

• A complex periodic sound has a pitch that corresponds to its fundamental frequency.

• Example: Musicians with perfect pitch can identify notes without reference tones.

Audiology and Sound Processing

Psychological vs Physical Attributes

• Audiology involves both physical sound measurements and psychological perceptions of sound (loudness).

• Example: A hearing impaired individual may report sounds as too soft is a psychological assessment.

Transient Distortion

Effects of Duration on Perceived Pitch

• Short duration sounds lead to transient distortion; this alters perceived pitch.

• Example: A 1000 Hz tone lasting 40 milliseconds may be heard as significantly different from longer durations (e.g., 3-4 seconds).

Duration and Pitch Perception

• Graph indicates that as the duration of a sound decreases below 100 milliseconds, perceived pitch declines.

• With a 1000 Hz sound lasting only 15 milliseconds, pitch might be perceived as closer to 900 Hz.

• Longer durations are required for lower frequencies to establish clear pitch.

Intensity and Pitch Perception

Investigation of Intensity Effects

• High intensity vs low intensity of the same sound can lead to different perceived pitches.

• Example Data: 150 Hz tone has decreasing pitch perception with increased intensity levels.

• Mid-range frequencies show less susceptibility to intensity changes.

Research on Frequency and Pitch

Scale of Pitch Perception

• Pitch perception is not a linear scale:

  • Example: Doubling pitch frequency does not equate to doubling perceived pitch.

  • Nonlinear Relationship: 1000 Hz and 2000 Hz do not equate to 1000 MELs and 2000 MELs.

Measurement of Pitch with Research

• Research methods involve presenting a standard tone to participants and adjusting variables to obtain thresholds of perception.

• Participants may identify whether a variable tone is higher or lower than a fixed tone, leading to data collection.

Development of Normative Data for Speech

• Researchers have created age-specific norms indicating expected performance levels in speech for children of various ages, guiding clinical assessments.

Frequency Range and Perceived Pitch

• The human hearing range is 20 Hz - 20,000 Hz, while perceived pitch is limited to approximately 0-3500 MELs.

• Confirmed that frequency to MEL relationship is non-linear.

Loudness Perception and Equal Loudness Curves

Phones and Equal Loudness Curves

• Phones: Unit of loudness level (like MELs for pitch).

• Equal Loudness Curves: Variation in decibel levels provides the same perceived loudness across frequencies.

  • Example: Need higher levels of intensity for low frequencies (e.g., 100 Hz) compared to mid or high frequencies.

Applications in Audiology

• In test scenarios, differences in intensity perceived between frequencies help evaluate hearing capabilities.

• Results of loudness perception highly depend on context and setting such as auditory testing compared to natural environments.

Spatial Perception of Sound

Localization and Lateralization

• Localization: Ability to locate sounds comes from external sources; often not achievable with headphones.

• Lateralization: Perception of sound direction through headphones.

• Techniques for sound localization include measuring interaural time differences (ITD) and interaural level differences (ILD).

The Role of the Pinna and Binaural Hearing

• The shape of the ear funnels sounds and assists in localizing sound directions.

• Binaural Summation Effect: Using two ears increases perceived loudness.

Signal Processing and Auditory Testing

• Patient responses in audiometric classes reflect various response types (hit, miss, false positive, false negative).

• Importance of sensitivity and specificity values in test accuracy is highlighted, especially in clinical settings.

Considerations on Testing Environments

• The transition from theoretical sound perception to practical applications in audiology demonstrates real-world implications for hearing perceptions and disorders.

• Reflection Effects: The Haas effect and first wavefront principle highlight the influence of environmental acoustics on sound perception.