2. Introduction Research Methods Fall 2010 Tamás Bőhm

3. What is psychophysics? Subdiscipline of experimental psychology Measuring the relationship between physical stimuli and their subjective correlates (percepts) Physical dimensions: light intensity, sound intensity, sound frequency etc. Subjective/perceptual dimensions: brightness, loudness, pitch, etc. Psychophysics: usually refers to vision Psychoacoustics: hearing

4. Why do we need psychophysics? Physical dimensions ≠ perceptual dimensions Light intensity ≠ brightness http://web.mit.edu/persci/people/adelson/

5. Why do we need psychophysics? Physical dimensions ≠ perceptual dimensions –If you double the intensity of a tone, you won’t hear it twice as loud! (only 60% louder) –If you change the frequency of a tone, loudness will also change (loudness depends both on intensity and on frequency) Sound intensity ≠ loudness

6. Why do we need psychophysics? Physical dimensions ≠ perceptual dimensions

7. Some practical uses Absolute threshold of hearing

8. Some practical uses Aging and the absolute threshold of hearing Wikipedia

9. Some practical uses Hearing aids: compensating for audibility loss by measuring individual audibility curves pure-tone audiometry Fletcher, 1929

10. Some practical uses Mp3 music coding: 1:10 compression by applying results from psychoacoustics –Absolute and difference thresholds –Properties of binaural hearing (joint stereo) –Masking effects

11. Some practical uses Military camouflage: detectability of patterns (different shapes and colors) from different viewing distances, under different conditions