Looking at sound Sound can be made visible by waveforms and spectrograms Speech sounds are created by vibrations of the vocal cords, which produce a wave Variation in air pressure The air pressure can be plotted into a graph to produce a waveform How did we get this wave? Time Pressure Production of sound waves by a loudspeaker Sound waves are like waves in a coil (like a Slinky) The individual air molecules only vibrate back and forth locally, they do not travel from the source to the receiver The red line is like your vocal cords Measuring the wave (pressure) Loudness depends primarily on the amplitude Time Pressure The sound wave of articulated Complex waves The sound wave of speech is much more complex than the waves weve seen so far The wave of a speech sound is always a combination of multiple other waves with different frequencies and different loudness These waves are added up Adding waves This is how a synthesizer works Frequencies To see which sound is produced, we cant just look at the waveform itself We need to find the different waves in the waveform More specifically, we need the frequencies of those waves Frequency is the number of times one wavelength comes by in one second If it comes by 10 times per second, its frequency is 10 Hertz (Hz) Humans can hear 20 to 20,000 Hz. Most phonetic information is below 8,000 Hz. Which wave has a higher frequency? 0 sec 1 sec2 sec3 sec4 sec Spectrograms The waveform can be analyzed into its frequencies Frequencies can be made visible with spectrograms Time Frequency articulated Time Frequency Dark areas indicate louder frequencies Voiced sounds have three or four major frequencies F1 articulated F0 F2 F3 d rr thth k yu ley d rr Time Frequency You can recognize vowels thth k articulated yu ley Time Frequency You can recognize stops: /p, t, k, b, d, g, / articulated d rr thth k yu ley d Time Frequency You can recognize aspiration Little puff of air Big puff of air articulated rr thth k yu ley Time Frequency articulated You can recognize pitch d rr thth kyu ley yu ley Which word is this? a.whose b.pseudonym c.judgment d.dessert How did you know? What would you do? Your students consistently pronounce this as /d s/. Your students consistently pronounce back as /b k/. Your students have a tendency to insert // between words in phrases like cold, drink, wet towel, and gas station. A student asks you for advice, saying: People cant tell whether Im saying thirteen or thirty. What should I do? One of your ESL students has many young American peers who regularly use rising intonation with statements. This student asks you about the conflict between this observation and what has been taught in the class. Next week Submit or hand in midterm assignment On BB or in class March 18, at beginning of class Lab session in PH212 at 6:45pm