PSYCHOACOUSTICS: Intensity, frequency, and temporal perception

Question 1

what are some ways to analyse and display sound?

Answer 1

• Overall intensity or amplitude
• Time-domain waveform: instantaneous magnitude change over time
• Frequency spectrum: magnitude of each frequency
• Spectrogram

Question 2

what information does the waveform of a time domain give us?

Answer 2

• Overall intensity of the sound
• How amplitude of sound changes instantaneously from moment to moment

Question 3

what information do we get from sound signals in frequency domain when examining the spectrum?

Answer 3

• Spectrum gives us the amplitude of each frequency, we can tell which frequencies have greater amplitude.
• We can also tell if there is harmonicity in the sound based on the spectrum.
  we look for regularly spaced peaks in the frequency domain. If these peaks occur at integer multiples of a fundamental frequency, it indicates harmonicity.

Question 4

what information can we get from sound signals in spectrotemporal domain in a spectrogram?

Answer 4

-the amplitude, the darkness of colour indicates amplitude

Question 5

why is that in a spectrogram, spectra is stacked over time?

Answer 5

• Spectrogram: A spectrogram is a visual representation of the frequency content of a signal over time. It is often used to analyze signals that vary in frequency and amplitude over time, such as speech or music.
• Stacking Spectra: Each spectrum represents the frequency content of the signal at a specific moment in time. By stacking multiple spectra one after another, we can visualize how the frequency content of the signal changes over time.

Question 6

what is the absolute threshold?

Answer 6

• The absolute threshold is the lowest level (overall intensity) of an auditory stimulus that is audible.
• It’s also the measurement of hearing sensitivity or audibility.
• In audiometric test, hearing sensitivity concerns with sinusoidal stimulation – pure tones.

Question 7

What are the three types of measurements used in auditory testing?

Answer 7

-minimum auditory field (MAF)
-minimum auditory pressure (MAP)
-hearing level (HL)

Question 8

what is minimum auditory testing (MAF)?

Answer 8

Minimum auditory field (MAF) where the sound is played in a free-field.

Question 9

what is minimum auditory pressure (MAP)?

Answer 9

Minimum auditory pressure (MAP) where the sound is typically played over headphones and the minimum audible pressure is measured at the tympanic membrane.

Question 10

what is hearing level (HL)?

Answer 10

Hearing level (HL) where the measure is based on an estimate of the minimum audible pressure at the tympanic membrane

Question 11

explain how Minimum Auditory Field (MAF) works:
- presentation method
- testing environment
- listener setup
-binaural listening
- calibrations

Answer 11

• Presentation Method: Sounds are played through a loudspeaker to simulate real-world listening conditions.
• Testing Environment: The testing environment is acoustically treated to minimize reflections, ensuring that the listener hears only the direct sound from the loudspeaker.
• Listener Setup: The listener typically faces the loudspeaker at a standardized distance of 1 meter. This allows for consistent testing conditions across different trials and participants.
• Binaural Listening: Both ears of the listener are used during the testing process, replicating natural listening conditions.
• Calibration: Before testing begins, the sound field is calibrated using a microphone placed at the position of the listener’s head. This ensures that the sound pressure level (SPL) at the listener’s position is accurately measured and controlled.

Question 12

what are the limitations of Minimum Auditory Field (MAF)

Answer 12

While MAF provides a standardised testing environment, it doesn’t fully account for the effects of the listener’s torso, head, and outer ears on sound perception. These diffraction effects can influence how sounds are perceived in real-world situations, leading to some discrepancies between MAF measurements and actual auditory experiences.

Question 13

explain how Minimum Auditory Pressure (MAP) works:
- threshold measurement
- monoaural presentation
- exclusion of head diffraction and ear canal resonance effects

Answer 13

• Threshold Measurement: MAP measures auditory thresholds in terms of Sound Pressure Level (SPL) at the listener’s tympanic membrane. This is typically achieved using a probe microphone placed near the eardrum to directly measure the sound pressure level reaching the inner ear.
• this is an advantage of MAP as it allows for precise control over sound presentation
• Monaural Presentation: Sounds are usually presented monaurally (to one ear) using headphones. This allows for precise control over the sound level reaching the ear being tested.
• Exclusion of Head Diffraction and Ear Canal Resonance Effects: Because the sound is presented through headphones, effects such as head diffraction (how the shape of the head affects sound propagation) and ear canal resonance (resonant frequencies within the ear canal) are not taken into account. This simplifies the testing process but may lead to some inaccuracies, particularly at higher frequencies where these effects are more pronounced.

Question 14

what are some challenges with the Minimum Auditory Pressure (MAP) method?

Answer 14

Reliable measurement of SPL at the tympanic membrane can be challenging due to factors such as the positioning of the probe microphone and the presence of standing waves in the ear canal, especially at higher frequencies. Variations in probe-microphone position can affect the accuracy of high-frequency measurements.

Question 15

compare MAF and MAP

Answer 15

• The MAP is typically 5 -10 dB higher than the MAF.
• 2-3 dB of this difference can be accounted for binaural summation: for the MAF listeners use two ears and for the MAP they use one.
• Physiological noise also contributes to low frequency difference – occlusion effect
• MAF includes the effect of reflections from the listeners head and shoulders. MAP doesn’t.
• MAF includes ear-canal resonance. MAP doesn’t.
• Ear-canal resonance at 3-4 kHz results in an increase of SPL

Question 16

what is the true limit of low frequency hearing?

Answer 16

The true limit of low frequency hearing is about 16 to 20 Hz. Below this, the threshold level for sensation is so intense that it may actually be felt rather than heard.

• In situations where very low-frequency sounds are perceived, they may actually be generated as distortion components at higher frequencies. So, while the perceived sensation may seem to originate from low frequencies, it’s actually a result of the distortion produced at higher frequencies.

Question 17

what is the upper frequency limit of hearing? (adults + children)

Answer 17

• The upper frequency limit of hearing is about 16 to 20 kHz.
• Young children can often hear tones as high as 20 kHz, but for most adults the threshold rises rapidly above 15 kHz.

Question 18

What is sensation level (SL) in psychophysical experiments, and how is it measured?

Answer 18

• Sensation level (SL) refers to the level of a stimulus relative to the individual listener’s threshold for that stimulus.
• It is typically measured in decibels (dB SL). For example, if a listener has a threshold of 40 dB SPL for a 1-kHz pure tone, and a 1-kHz pure tone is presented at 60 dB SPL, the sensation level would be 20 dB.

Question 19

why do we not use MAF and MAP with patients and what do we use instead?

Answer 19

-MAF and MAP enable accurate measurement of auditory sensitivity. BUT The problem with both MAF and MAP thresholds is that they are difficult and time consuming to measure accurately.

• SO To get round these difficulties we instead measure the Reference Equivalent Sound Pressure Level (RETSPL) for the particular headphones and measure the threshold relative to that for young otologically normal listeners, that is as a hearing level (dB HL).

Question 20

how does physiological vulnerability affect sensitivity?

Answer 20

• evidence that the outer hair cells in the inner ear are physiologically very vulnerable and hearing can be affected by:

-Noise exposure
-Ototoxic drugs
-Hypoxia

• The effect can be evident as a change in absolute sensitivity

Question 21

what causes Noise-induced hearing loss (NIHL) and how does it look on an audiogram?

Answer 21

• Even mild hearing-loss is associated with damage to OHCs. The damage occurs first at the places that correspond to the ear-canal resonance. Can be temporary threshold shift or permanent
• Results in a 2 - 4 kHz notch in the PTA

Question 22

how does the audiogram look for an age related hearing loss?

Answer 22

a downward ski slop, getting worse at high frequencies

Question 23

what effect does the stimulus duration have on threshold?

Answer 23

Duration affects threshold – longer stimuli tend to have lower thresholds.

Question 24

how do we investigate the effect of duration on threshold?

Answer 24

1) Keep the signal power (intensity) constant, (watts, W/m2)
2) keep the signal energy constant (power=energy/time)

e.g. if we have a 1-second sound at 50 dB SPL (sound pressure level), and we want to keep the intensity constant, if we double the duration to 2 seconds, we’d need to halve the power to maintain the same intensity level. and we do the same for signal energy

Question 25

what effect does duration have on threshold?

Answer 25

• For tones lasting below 200 milliseconds (ms), longer tones tend to have lower thresholds.
• This means that shorter tones need to be louder for detection compared to longer tones.
• However, above 200 ms, the effect of tone duration on threshold becomes less apparent.
• This implies that once the tone duration exceeds 200 ms, the improvement in threshold with increasing duration becomes less significant.

Question 26

what is the the duration recommendation for audiometric testing?

Answer 26

• To ensure accurate threshold determination during audiometric testing, it’s advised to present tones longer than 200 ms.
• By presenting tones longer than 200 ms, audiologists can minimize the variability in threshold measurements associated with shorter tone durations and ensure more reliable results.

Question 27

How does the ear respond to stimuli of different durations?

Answer 27

Between 20 and 200 milliseconds, the ear acts as a constant energy detector, requiring a consistent energy level for detection.

Question 28

What is temporal integration in auditory perception?

Answer 28

Temporal integration refers to the process where stimuli of varying durations require a critical amount of energy to reach detection threshold. If a stimulus’s duration is halved within a certain range, its power must double to reach detection threshold.

Question 29

What is the integration window in auditory perception?

Answer 29

The integration window is the time limit over which the cochlea integrates neural activity to detect stimuli. For sine waves, this window is approximately 300 milliseconds, but it varies depending on the frequency of the stimulus.

Question 30

what is the range of human hearing?

Answer 30

The typical range of human hearing is from 20 Hz to 20 kHz, but it’s most sensitive to sounds between 1 and 4 kHz. This sensitivity is influenced by equal loudness contours, which means that even at the same intensity level (measured in dB SPL), sounds within this range are perceived as louder compared to sounds at other frequencies.

Question 31

How do detection thresholds vary at different frequencies?

Answer 31

Detection thresholds vary depending on frequency. For example, listeners can detect sounds as low as 0 dB SPL at 3 kHz, but they require a much higher intensity (40 dB SPL) at 100 Hz.

Question 32

What is frequency discrimination, and how does it change with frequency?

Answer 32

Frequency discrimination refers to the ability to distinguish between two tones based on their frequencies. At 3 kHz, listeners can distinguish frequencies that differ by less than 0.3%, whereas at 100 Hz, this threshold increases to 3%.

Question 33

How does loudness discrimination vary with changes in signal amplitude?

Answer 33

Listeners can detect changes in loudness when the signal is altered by about 1 dB, corresponding to approximately a 12% change in amplitude.

Question 33

Why do we need to know about sensitivity?

Answer 33

• What are the limits of normal human auditory sensitivity?
• What is the lowest intensity we can hear?
• What range of frequencies can we hear?
• To determine what is not normal.
• For design of audio equipment.
• For design of hearing aids / cochlear implants.
• To know how much to compensate for hearing loss.
• To get a better understanding of the auditory system

Question 34

what is auditory discrimination?

Answer 34

Hear a change in the acoustic feature of a sound

Discrimination is
- not about whether the sound can be heard or not (which concerns audibility or sensitivity)
- but about whether a (perfectly audible) sound changes in any physical dimension.

Question 35

what is intensity discrimination?

Answer 35

ability to Discriminate whether two sound is different in levels

Question 36

What is Weber’s law?

Answer 36

change in a stimulus that will be just noticeable is a constant ratio of the original stimulus. The ratio does not change

e.g. you’ll notice a small change in a dim light easily, but you might need a bigger change to notice it in a bright light

Question 37

what is meant by a near miss to Webers law?

Answer 37

Near-Miss to Weber’s Law: The near-miss to Weber’s law refers to a phenomenon where intensity discrimination improves at higher intensities, contrary to what Weber’s law predicts. Instead of a horizontal flat line (indicating consistent discrimination ability across all intensity levels), the data show an improvement in intensity discrimination at higher intensities.

Question 38

how is loudness perception expressed?

Answer 38

Expressed in Phon

Question 39

explain the Phon scale?

Answer 39

The Phon scale provides with a basic scale of loudness. It tells us that one sound is louder than another.

e.g. 40 Phon is defined as the loudness perceived for a 40-dB SPL 1kHz tone.

Question 40

How is loudness expressed?

Answer 40

Loudness can also be expressed in Sone

Question 41

explain the Sone scale?

Answer 41

The Sone scale tells us how much louder one sound is than another (twice as loud, four times as loud, etc.)

Question 42

How does the loudness of a 50-phon sound compare to that of a 40-phon sound?

Answer 42

A 50-phon sound is twice as loud as a 40-phon sound.

Question 43

what is the impact of hearing impairment on loudness perception?

Answer 43

• Reduced dynamic range because of elevated absolute threshold
• Loudness increases very rapidly for hearing impaired listeners
• Cochlear hearing loss isassociated with abnormal loudness perception. Detection thresholds are elevated, but the level of sound that is found uncomfortably loud is elevated by a smaller amount
• Could be a contributor to poor speech in noise due to the discomfort caused by the abnormal loudness growth

Question 44

what is pulse duration?

Answer 44

Pulse duration refers to the length of time a signal or stimulus is present or active. In the context of auditory stimuli, pulse duration often refers to the duration of a brief sound or tone presented to the listener. It indicates how long the sound or tone lasts before it ends. Typically, shorter pulse durations indicate briefer sounds, while longer pulse durations indicate longer-lasting sounds.

Question 45

How is frequency discrimination affected by the duration of the signal?

Answer 45

The duration of the signal affects frequency discrimination. Generally, shorter signals result in worse frequency discrimination abilities compared to longer signals.

Question 46

What does DLF measure in frequency discrimination?

Answer 46

DLF, or Difference Limen for frequency, measures the ability to discriminate between a change in frequency as a function of pulse duration.

Question 47

How is DLF typically expressed?

Answer 47

DLF is typically expressed as a percentage of the center frequency.

Question 48

What is pitch, and how does it relate to auditory sensations?

Answer 48

Pitch is one of the primary auditory sensations, alongside loudness and timbre. It refers to the perceived frequency of a sound wave and is associated with the sensation of highness or lowness in tone.

Question 49

How does pitch play a role in music and speech?

Answer 49

In music, sequences of pitch define melody, while simultaneous combinations of pitch define harmony. In speech, rising and falling pitch contours help define prosody. In tone languages like Mandarin and Cantonese, pitch contours help differentiate the meanings of words.

Question 50

What is the perceptual correlate of pitch?

Answer 50

Pitch is the perceptual correlate of the periodicity, or repetition rate, of an acoustic waveform. It refers to how frequently a sound wave repeats over time and is perceived as the highness or lowness of a sound.

Question 51

what are some sounds that evoke perception of pitch?

Answer 51

Sound that evokes perception of pitch can be

• A pure tone
• A harmonic complex tone
• Sometimes a series of narrow band noise with center frequencies aligned on a musical scale can also induce the perception of pitch

Question 52

What is the “missing fundamental phenomenon” associated with HCT?

Answer 52

The “missing fundamental phenomenon” refers to the perception of a pitch percept, even when the fundamental frequency (F0) component is missing or masked in a harmonic complex tone. Despite the absence of the fundamental frequency, listeners still perceive a pitch corresponding to the frequency of the missing fundamental.

Question 53

Where are Harmonic Complex Tones commonly found?

Answer 53

Harmonic Complex Tones are ubiquitous in speech, music, and animal vocalizations.

Question 53

What are Harmonic Complex Tones (HCT)?

Answer 53

Harmonic Complex Tones (HCT) are sounds where all frequency components are integer multiples of a common fundamental frequency (F0).

Question 54

What is the purpose of the Gap detection threshold?

Answer 54

• The Gap detection threshold is designed to identify the presence of a silent gap between two sounds.
• Individuals with either poorer temporal integration (characterized by a longer temporal integration window) or finer temporal resolution (a shorter temporal integration window) will detect the gap.