Prof. Greg Francis Sound Quality PSY 310 Greg Francis Lecture 32 Name that tune! Sound perception An integral part of our modern world Billions are spent annually on Creation of new sounds or sound sequences (music) Equipment to play sounds (ipods, speakers, stereo systems, surround sound theater systems) Buildings to present sounds (opera houses, symphony halls, recording studios) People who are gifted with sound (singers, musicians, song writers) This is true all over the world Much of the emphasis is to get quality sound But what does this mean? 1
Quality terms For stereo systems, many terms used to describe quality have to do with the frequencies of sound that are generated and/or the location of sounds A system cannot produce all frequencies equally well Here s some common terms for stereo speakers and what they mean Forward (Recessed): vocals, male and female, tend to be very present (absent), located in front (behind) the speakers Spacious, airy, open: the sense of space present around the instruments and singers Closed, muted, dry: indicate the midrange and treble frequencies are rolled off or depressed and dull Rich: full, rounded sound with lots of deep, sonorous bass Quality terms Sibilant: the speaker has a midrange/treble peak that emphasizes the "sss" and "ttt" sounds of singers vocals Strident: way too much treble output, making brass and string sound shrill or harsh Thin: means the speaker has little or no bass output Boomy: has too much bass that dominates its sound Punchy: powerful upper bass, like a disco, but no really deep bass Muddy: the midrange isn t clear; that it s hard to separate the distinct contributions of male and female singers in a chorus Suck-out: valley or other uneven response in mid-range frequencies Nasal: what a midrange peak does to vocals, like what happens to your voice when you cup your hands around your mouth while you re speaking. 2
Prof. Greg Francis Music We already noted that different instruments sound different in large part because they include sounds of frequencies other than the main sound In addition, notes on an instrument include: Attack: the buildup of sound at the beginning of the tone Decay: the decrease in sound at the end of a tone We are very sensitive to these aspects of sound, even if we don t know what we are sensitive to Johann Sebastian Bach. The Well-Tempered Clavier, Book 1, Prelude 1 (in C major) Demonstration of piano Rooms where sound is very important must be designed to promote quality sound Need to avoid echo and problem reverberations It s a difficult problem, and expensive to repair Often start with a model (1:50 scale) Present sounds of different frequencies and measure the sound at different places in the model 3
A sound (like a gunshot) at the stage has multiple effects An acoustical engineer can identify which part of the hall contributes to different reverberations and introduce new elements to stop echo 4
You want some reverberation, else the sound seems flat Different parts of the hall contribute to the reverberations The models can match the actual structure quite well 5
Auditory grouping We noted that sounds all come together on the basilar membrane How do we track one sound stream? Similar to the issue faced by visual grouping Gestalt laws Auditory stream segregation Identification of different perceptual streams of sounds Location: sounds from the same place, come from the same source Similarity of timbre (complex sound): sounds of similar timbre come from the same source Similarity of pitch (Pitch demo): similar pitches come from the same source Auditory grouping Temporal proximity: sounds in rapid progression tend to be from the same source Onset and offset: sounds that stop and start at different times tend to be from different sources Good continuation (Demo, Leyenda): sounds that stay constant or change smoothly are often produced by the same source Experience (Mystery song): you can perceptually group sounds together if know how they should be grouped 6
Vision and audition Often times vision and audition work together to produce a unified perceptual experience Vision can help guide auditory grouping Sound can help guide visual grouping Sometimes they conflict McGurk effect demo Conclusions Lots of issues in sound quality Complicated engineering Involve both physical space Temporal grouping 7
Next time Review for Exam 3 Take exam 3 Finish up the course with Touch Smell Taste 8