How do we perceive speech?
Vowels are perceived based off of their formants, which are visible on a spectrogram. To the left is a spectrogram, showing the formants of the phrase "she sells sea shells" Formants are shown on the spectrogram based on what the articulators in the mouth (ie tongue, lips) are doing during speech. To understand the formants of vowels, try saying the phoneme /i/, as in the vowel in the word "tea." Notice how your tongue is placed high and forward in your mouth? Now try saying the phoneme /o/, as in the vowel in the word "toe." Try to feel your tongue placement, as it should be high and forward in the mouth for /i/, and in the back of your mouth for /o/. The most important formants in vowel perception are formants 1 and 2, which are labeled as F1 and F2. F1 is inversely related to tongue height, while F2 is directly related to tongue advancement. For example, the phoneme /i/ has a high tongue height, and a forward tongue advancement, therefore, its F1 would be low and its F2 would be low.
Consonants are classified by their place of articulation, manner of articulation, and voicing. Place of articulation refers to where the articulation is occurring, while manner of articulation refers to how. Take the phoneme /p/ for example as in the word "put." Its place of articulation is the lips, and its manner is a known as a "stop" because the air is constricted then released behind the lips. Now say /p/ again and gently touch the front of your neck, where your voice box is located. Compare it to the phoneme /b/ as in "bug," and alternate saying these two phonemes /p/ and /b/. Notice how the /p/ has no vibrations, but the /b/ does? This pertains to voicing. Voiced consonants vibrate, while unvoiced consonants do not. We can see characteristics of consonants such as their place, manner, and voicing on the spectrogram and can also identify consonants based off of the transitions between formants.
How do we perceive music?
Musical instruments have different frequencies depending on their shape and size. Notice how when a "C" is being played on the guitar, and a "C" is being played on the flute, that even though the instruments are playing the same note, they sound different? This is how we can distinguish between which instrument is playing while listening to a musical recording. The characteristic frequency of a guitar is much lower than that of a flute. Think about the voice of an adult male versus the voice of an adult female. Their vocal tracts and voice boxes differ in shape and size, and their voices differ in characteristic frequency, with the male's voice typically being perceived as lower. Taking the example of musical instruments, think of this male and female singing the same note. Even though it is the same note, they will sound different. Pitch is our perception of frequency.
How is our perception altered if outer hair cell loss occurs?
Due to the active mechanism being the primary function of the OHCs, we would lose that extra amplification, or boost, of incoming sound. People with OHC loss would not have amplification of the characteristic frequency of the musical instruments playing, making it difficult for them to distinguish between instruments while listening to an orchestra.
As for speech, it would be difficult to distinguish between some phonemes. Distinguishing between vowels would be difficult because of their formant positions. For example, the word "bit" could be interpreted as "beat," and vice versa, because their F1 and F2s are similar.
As for consonants, it would be difficult for those with OHC loss to distinguish between the place of articulation of the phoneme. For example, they may hear "ba" as "ga," having difficultly distinguishing between the bilabial /b/ (produced by the lips) and the velar /g/ (produced with the velum, also known as the soft palate).
In summary:
Vowels are perceived based off of their formants, which are visible on a spectrogram. To the left is a spectrogram, showing the formants of the phrase "she sells sea shells" Formants are shown on the spectrogram based on what the articulators in the mouth (ie tongue, lips) are doing during speech. To understand the formants of vowels, try saying the phoneme /i/, as in the vowel in the word "tea." Notice how your tongue is placed high and forward in your mouth? Now try saying the phoneme /o/, as in the vowel in the word "toe." Try to feel your tongue placement, as it should be high and forward in the mouth for /i/, and in the back of your mouth for /o/. The most important formants in vowel perception are formants 1 and 2, which are labeled as F1 and F2. F1 is inversely related to tongue height, while F2 is directly related to tongue advancement. For example, the phoneme /i/ has a high tongue height, and a forward tongue advancement, therefore, its F1 would be low and its F2 would be low.
Consonants are classified by their place of articulation, manner of articulation, and voicing. Place of articulation refers to where the articulation is occurring, while manner of articulation refers to how. Take the phoneme /p/ for example as in the word "put." Its place of articulation is the lips, and its manner is a known as a "stop" because the air is constricted then released behind the lips. Now say /p/ again and gently touch the front of your neck, where your voice box is located. Compare it to the phoneme /b/ as in "bug," and alternate saying these two phonemes /p/ and /b/. Notice how the /p/ has no vibrations, but the /b/ does? This pertains to voicing. Voiced consonants vibrate, while unvoiced consonants do not. We can see characteristics of consonants such as their place, manner, and voicing on the spectrogram and can also identify consonants based off of the transitions between formants.
How do we perceive music?
Musical instruments have different frequencies depending on their shape and size. Notice how when a "C" is being played on the guitar, and a "C" is being played on the flute, that even though the instruments are playing the same note, they sound different? This is how we can distinguish between which instrument is playing while listening to a musical recording. The characteristic frequency of a guitar is much lower than that of a flute. Think about the voice of an adult male versus the voice of an adult female. Their vocal tracts and voice boxes differ in shape and size, and their voices differ in characteristic frequency, with the male's voice typically being perceived as lower. Taking the example of musical instruments, think of this male and female singing the same note. Even though it is the same note, they will sound different. Pitch is our perception of frequency.
How is our perception altered if outer hair cell loss occurs?
Due to the active mechanism being the primary function of the OHCs, we would lose that extra amplification, or boost, of incoming sound. People with OHC loss would not have amplification of the characteristic frequency of the musical instruments playing, making it difficult for them to distinguish between instruments while listening to an orchestra.
As for speech, it would be difficult to distinguish between some phonemes. Distinguishing between vowels would be difficult because of their formant positions. For example, the word "bit" could be interpreted as "beat," and vice versa, because their F1 and F2s are similar.
As for consonants, it would be difficult for those with OHC loss to distinguish between the place of articulation of the phoneme. For example, they may hear "ba" as "ga," having difficultly distinguishing between the bilabial /b/ (produced by the lips) and the velar /g/ (produced with the velum, also known as the soft palate).
In summary:
- we perceive vowels primarily by their formants F1 and F2
- we perceive musical instruments based off of their characteristic frequency (pitch)
- OHC loss would affect a person's perception of speech - particularly vowels with similar formants and place of articulation for consonants
- OHC loss would affect a person's perception of music - particularly their ability to distinguish between musical instruments