{"id":134,"date":"2024-03-22T10:40:42","date_gmt":"2024-03-22T14:40:42","guid":{"rendered":"https:\/\/opentextbc.ca\/psychologymtdi\/chapter\/psychophysics\/"},"modified":"2024-08-22T16:26:07","modified_gmt":"2024-08-22T20:26:07","slug":"psychophysics","status":"publish","type":"chapter","link":"https:\/\/opentextbc.ca\/psychologymtdi\/chapter\/psychophysics\/","title":{"raw":"Psychophysics","rendered":"Psychophysics"},"content":{"raw":"

[pb_glossary id=\"595\"]Approximate reading time:[\/pb_glossary] 35 minutes<\/p>\nLet\u2019s focus on how we see light and hear sound. Both of these come to us in waves, but they are different kinds of waves. Even though they are different, these waves have some things in common that are important for how we see and hear.\n\nWhen we talk about waves, we look at two main things: amplitude and wavelength. Amplitude<\/strong> is how high or low the wave goes. Imagine a wave in the ocean: the amplitude is the height from the middle of the wave to the top. Wavelength<\/strong> is how long the wave is from one peak to the next (Figure SP.3).\n\n[caption id=\"attachment_133\" align=\"aligncenter\" width=\"651\"]\"A Figure SP.3. Amplitude and wavelength.<\/strong> The amplitude or height of a wave is measured from the crest to the trough. The wavelength is measured from peak to peak.[\/caption]\n\nThese two things, amplitude and wavelength, help us understand things like how loud a sound is or what colour something is. For example, a loud sound has a high amplitude. The colour red has a long wavelength, while blue has a shorter one (Figure SP.4).\n\n[caption id=\"attachment_133\" align=\"aligncenter\" width=\"510\"]\"Stacked Figure SP.4. Wavelengths and frequencies.<\/strong> This figure illustrates waves of differing wavelengths\/frequencies. At the top of the figure, the red wave has a long wavelength\/short frequency. Moving from top to bottom, the wavelengths decrease and frequencies increase.[\/caption]\n\nIn this section, we're going to learn more about how waves work and how they affect what we see and hear. Remember, even though this might sound complex, it's all about understanding the waves that make up the sights and sounds around us.\n

Sound Waves<\/h1>\nThe physical properties of sound waves are associated with various aspects of our perception of sound. The frequency of a sound wave is associated with our perception of that sound\u2019s\u00a0pitch. We measure sound in hertz (Hz), which tell us how many waves pass a point in a second. High-pitched sounds have a lot of waves in a second (high frequency), and low-pitched sounds have fewer (low frequency). In humans, the audible range of sound frequencies is between 20 and 20,000 Hz, with greatest sensitivity to those frequencies that fall in the middle of this range.\n\nOther species show differences in their audible ranges. For instance, chickens have a very limited audible range, from 125 to 2000 Hz. Mice have an audible range from 1000 to 91,000 Hz, and the beluga whale\u2019s audible range is from 1000 to 123,000 Hz. Our pet dogs and cats have audible ranges of about 70\u201345,000 Hz and 45\u201364,000 Hz, respectively (Strain, 2003).\n\nThe loudness<\/strong> of a given sound is closely associated with the amplitude of the sound wave. Higher amplitudes are associated with louder sounds. Loudness is measured in terms of\u00a0decibels (dB), a unit of sound intensity. A typical conversation would correlate with 60 dB; a rock concert might check in at 120 dB (Figure SP.9). A whisper 5 feet away or rustling leaves are at the low end of our hearing range; sounds like a window air conditioner, a normal conversation, and even heavy traffic or a vacuum cleaner are within a tolerable range. However, there is the potential for hearing damage from about 80 dB to 130 dB: These are sounds of a food processor, power lawn mower, heavy truck (25 feet away), subway train (20 feet away), live rock music, and a jackhammer. About one-third of all hearing loss is due to noise exposure, and the louder the sound, the shorter the exposure needed to cause hearing damage (Le, Straatman, Lea, & Westerberg, 2017). Listening to music through earbuds at maximum volume (around 100\u2013105 decibels) can cause noise-induced hearing loss after 15 minutes of exposure. Although listening to music at maximum volume may not seem to cause damage, it increases the risk of age-related hearing loss (Kujawa & Liberman, 2006). The threshold for pain is about 130 dB, which can be seen with a jet plane taking off or a revolver firing at close range (Dunkle, 1982).\n\n \n\n[caption id=\"attachment_133\" align=\"aligncenter\" width=\"975\"]\"This Figure SP.5. Sound and decibels.<\/strong> This figure illustrates the loudness of common sounds.[\/caption]\n\nWatch this video: Sound: Wavelength, Frequency and Amplitude. (6 minutes)<\/a>\n
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<\/div>\n<\/div>\nhttps:\/\/youtu.be\/TsQL-sXZOLc?si=Zxspv9QSRg5z2hTc\n\n\u201cSound: Wavelength, Frequency and Amplitude.\u201d video by Science Sauce is licensed under the Standard YouTube licence.<\/span>\n\nOf course, different musical instruments can play the same musical note at the same level of loudness, yet they still sound quite different. This is known as the timbre of a sound.\u00a0Timbre\u00a0refers to a sound\u2019s purity, and it is affected by the complex interplay of frequency, amplitude, and timing of sound waves. Sound, specifically hearing, will be discussed later in this section.\n

Light Waves<\/h1>\nThe\u00a0visible spectrum<\/strong>\u00a0is the portion of the larger\u00a0electromagnetic spectrum\u00a0that we can see. As\u00a0Figure SP.6 shows, the electromagnetic spectrum encompasses all of the electromagnetic radiation that occurs in our environment and includes gamma rays, x-rays, ultraviolet light, visible light, infrared light, microwaves, and radio waves. The visible spectrum in humans is associated with wavelengths that range from 380 to 740 nm \u2014 a very small distance, since a nanometer (nm) is one billionth of a metre. Other species can detect other portions of the electromagnetic spectrum. For instance, honeybees can see light in the ultraviolet range (Wakakuwa, Stavenga, & Arikawa, 2007), and some snakes can detect infrared radiation in addition to more traditional visual light cues (Chen, Deng, Brauth, Ding, & Tang, 2012; Hartline, Kass, & Loop, 1978).\n\n[caption id=\"attachment_133\" align=\"aligncenter\" width=\"975\"]\"This Figure SP.6. Visible spectrum.<\/strong> Light that is visible to humans makes up only a small portion of the electromagnetic spectrum.[\/caption]\n\nIn humans, light wavelength is associated with perception of colour (Figure SAP.11). Within the visible spectrum, our experience of red is associated with longer wavelengths, greens are intermediate, and blues and violets are shorter in wavelength. (An easy way to remember this is the mnemonic ROYGBIV:\u00a0red,\u00a0orange,\u00a0yellow,\u00a0green,\u00a0blue,\u00a0indigo,\u00a0violet.) The amplitude of light waves is associated with our experience of brightness or intensity of colour, with larger amplitudes appearing brighter. Brighter colours have higher amplitudes.\n\n[caption id=\"attachment_133\" align=\"aligncenter\" width=\"975\"]\"A Figure SP.7. Wavelengths and colours.<\/strong> Different wavelengths of light are associated with our perception of different colours.[\/caption]\n\n
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Watch this video: Sensation and Perception: Crash Course Psychology #5 (11 minutes)<\/a><\/div>\nhttps:\/\/youtu.be\/unWnZvXJH2o\n\n\u201cSensation and Perception: Crash Course Psychology #5\u201d video by CrashCourse is licensed under the Standard YouTube licence.\n

Image Attributions<\/h1>\nFigure SP.3. Figure 5.5 as found in Psychology 2e by OpenStax<\/a> is licensed under a CC BY 4.0 License<\/a>.\n\nFigure SP.4. Figure 5.6 as found in Psychology 2e by OpenStax<\/a> is licensed under a CC BY 4.0 License<\/a>.\n\nFigure SP.5. Figure 5.9 as found in Psychology 2e by OpenStax<\/a> is licensed under a CC BY 4.0 License<\/a> and contains modifications of the following works: \"planes\"<\/a> by Max Pfandl<\/a> is licensed under a CC BY 2.0 licence<\/a>; \"crowd\"<\/a> by Christian Holm\u00e9r<\/a> is licensed under a CC BY 2.0 licence<\/a>; \"earbuds\"<\/a> by Skinny Guy Lover<\/a> is in the public domain<\/a>; \"traffic\"<\/a> by islandworks<\/a> is licensed under a Pixabay license<\/a>; \"talking\"<\/a> by Joi Ito<\/a> is licensed under a CC BY 2.0 licence<\/a>; \"leaves\"<\/a> by Aurelijus Valei\u0161a<\/a> is licensed under a CC BY 2.0 licence<\/a>.\n\nFigure SP.6. Figure 5.7 as found in Psychology 2e by OpenStax<\/a> is licensed under a CC BY 4.0 License<\/a>.\n\nFigure SP.7. Figure 5.8 as found in Psychology 2e by OpenStax<\/a> is licensed under a CC BY 4.0 License<\/a> and contains modifications of the following works: \"Humanly Visible Spectrum<\/a>\" by Johannes Ahlmann<\/a> is licensed under a CC BY 2.0 licence<\/a>.","rendered":"

Approximate reading time:<\/a> 35 minutes<\/p>\n

Let\u2019s focus on how we see light and hear sound. Both of these come to us in waves, but they are different kinds of waves. Even though they are different, these waves have some things in common that are important for how we see and hear.<\/p>\n

When we talk about waves, we look at two main things: amplitude and wavelength. Amplitude<\/strong> is how high or low the wave goes. Imagine a wave in the ocean: the amplitude is the height from the middle of the wave to the top. Wavelength<\/strong> is how long the wave is from one peak to the next (Figure SP.3).<\/p>\n

\"A
Figure SP.3. Amplitude and wavelength.<\/strong> The amplitude or height of a wave is measured from the crest to the trough. The wavelength is measured from peak to peak.<\/figcaption><\/figure>\n

These two things, amplitude and wavelength, help us understand things like how loud a sound is or what colour something is. For example, a loud sound has a high amplitude. The colour red has a long wavelength, while blue has a shorter one (Figure SP.4).<\/p>\n

\"Stacked
Figure SP.4. Wavelengths and frequencies.<\/strong> This figure illustrates waves of differing wavelengths\/frequencies. At the top of the figure, the red wave has a long wavelength\/short frequency. Moving from top to bottom, the wavelengths decrease and frequencies increase.<\/figcaption><\/figure>\n

In this section, we’re going to learn more about how waves work and how they affect what we see and hear. Remember, even though this might sound complex, it’s all about understanding the waves that make up the sights and sounds around us.<\/p>\n

Sound Waves<\/h1>\n

The physical properties of sound waves are associated with various aspects of our perception of sound. The frequency of a sound wave is associated with our perception of that sound\u2019s\u00a0pitch. We measure sound in hertz (Hz), which tell us how many waves pass a point in a second. High-pitched sounds have a lot of waves in a second (high frequency), and low-pitched sounds have fewer (low frequency). In humans, the audible range of sound frequencies is between 20 and 20,000 Hz, with greatest sensitivity to those frequencies that fall in the middle of this range.<\/p>\n

Other species show differences in their audible ranges. For instance, chickens have a very limited audible range, from 125 to 2000 Hz. Mice have an audible range from 1000 to 91,000 Hz, and the beluga whale\u2019s audible range is from 1000 to 123,000 Hz. Our pet dogs and cats have audible ranges of about 70\u201345,000 Hz and 45\u201364,000 Hz, respectively (Strain, 2003).<\/p>\n

The loudness<\/strong> of a given sound is closely associated with the amplitude of the sound wave. Higher amplitudes are associated with louder sounds. Loudness is measured in terms of\u00a0decibels (dB), a unit of sound intensity. A typical conversation would correlate with 60 dB; a rock concert might check in at 120 dB (Figure SP.9). A whisper 5 feet away or rustling leaves are at the low end of our hearing range; sounds like a window air conditioner, a normal conversation, and even heavy traffic or a vacuum cleaner are within a tolerable range. However, there is the potential for hearing damage from about 80 dB to 130 dB: These are sounds of a food processor, power lawn mower, heavy truck (25 feet away), subway train (20 feet away), live rock music, and a jackhammer. About one-third of all hearing loss is due to noise exposure, and the louder the sound, the shorter the exposure needed to cause hearing damage (Le, Straatman, Lea, & Westerberg, 2017). Listening to music through earbuds at maximum volume (around 100\u2013105 decibels) can cause noise-induced hearing loss after 15 minutes of exposure. Although listening to music at maximum volume may not seem to cause damage, it increases the risk of age-related hearing loss (Kujawa & Liberman, 2006). The threshold for pain is about 130 dB, which can be seen with a jet plane taking off or a revolver firing at close range (Dunkle, 1982).<\/p>\n

 <\/p>\n

\"This
Figure SP.5. Sound and decibels.<\/strong> This figure illustrates the loudness of common sounds.<\/figcaption><\/figure>\n

Watch this video: Sound: Wavelength, Frequency and Amplitude. (6 minutes)<\/a><\/p>\n

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