Exam 4 Psych 333.docx - Chapter 11 LO 1 Describe the...

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Chapter 11 LO 1: Describe the physical stimulus for sound, including the concepts of sound waves, pure tones, amplitude, and frequency. o What is sound? Physically: pressure changes, usually in the air. Perceptually: how you make sense of it; experience; o Physical Stimulus How does this speaker produce sound? Diaphragm moves out, pushing air molecules together o Condensation Diaphragm also moves in, pulling air molecules apart o Rarefaction Creates alternating high- and low- pressure regions traveling through air (and other media). o Sound waves Bird song, car backfiring, Harley “rumble”, Human voice… All are comprised of these alternative waves. Sound travels faster through water than air 340 meters per second (air??) vs. 1500 meters per second (water??) Remember that the stimulus is pressure, not the air molecules themselves. Molecules bump into each other… Simplest form is a pure tone Sine wave, like seen at the right o E.g. Tuning fork Pure tone/ sine wave: Frequency: number of cycles within a given time period o Measured in Hertz (Hz): 1 Hz is one cycle per second o Perception of pitch is related to frequency Amplitude: o Difference between high and low peaks of the wave o Perception of amplitude= loudness Decibel (dB) is a measure of loudness dB is logarithmic (we won’t be computing) Complex tones? Both pure and some complex tones are periodic (repeat) tones. o Fundamental frequency is the repetition rate and is called the first harmonic o Periodic complex tones consist of a number of pure tones called harmonics
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o Additional harmonics are multiples of the fundamental frequency LO 2: Analyze how physical characteristics of the sound wave are related to the perceptual dimensions of loudness and pitch. o Blended into LO1 LO 3: Illustrate what an audibility curve is and how these curves are different for different species. o Remember thresholds?... Can you hear it? o Loudness and amplitude Perception of loudness is closely related to amplitude (or level) 0 dB Sound Pressure Level (SPL) around threshold for a human o Audibility Curve Frequency and dB SPL interact Not all frequencies are heard equally well Green = auditory response area; we can hear tones that fall in this area Red = equal loudness curve Curve marked “40” o Observers matched loudness of various frequencies to point C (40 dB @ 1,000 Hz) Species? Dogs can hear up to 40,000 Hz Cats can hear up to about 50,000 Hz or beyond Bats and Dolphins? Well above 100,000 Hz. LO 4: Define timbre, and discuss how timbre is related to perception of complex sounds. o Pitch The perceptual quality we describe as high and low (e.g. with voices) Again, roughly based on frequency o Timbre Tones that have the same loudness, pitch, and duration… But still sound different E.g., two pianos can both be in tune, but sound different (let alone vs. a guitar, oboe, etc)
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