As with any hearing test, the test equipment plays a sound for the subject to see if he/she will hear it. The central problem in testing the hearing of infants is determining whether or not they hear that particular sound. Of course it's easy with adults and school age children, you simply have them press a button every time they hear a sound. Ellie is not so cooperative. One way to detect whether or not she heard the sound is to play it so loud that she flinches. Aside from being very irritating for Ellie and her parents this wouldn't provide any information about how well she hears low volume sounds.
What we need is a magical way of determining when she heard something. As usual when magic is required we turn to electronics. In this particular case we also need the help of some modern neurobiology. When a person hears something the ears send electrical impulses to the brain via the nervous system. As it turns out these impulses can be detected by sensors similar to the ones used for Ellie's EKG leads.
As you can hopefully see in the picture the sensors are placed on Ellie's forhead (black), jaw (green) and at the base of her neck (white). (Click on the image to get a better view.) These sensors will detect the impulses in Ellie's brain stem. Then she is fitted with around-ear earphones. Finally the computer program plays a series of clicking noises. The clicking noises are all the same volume (35 dB) but in different patterns. The computer knows the pattern sounds that it has played and so it knows roughly what to expect from Ellie's brain stem. The software then "cross-correlates" what it expects with what it measures to determine whether or not Ellie heard the clicks.
Now I know you're all thinking it, so I'll just say it: Technology is so cool!
Wednesday, October 22, 2008
Tech Spotlight: Infant Hearing Test
If a Tree Falls in the Middle of a Forest ...
As with any hearing test, the test equipment plays a sound for the subject to see if he/she will hear it. The central problem in testing the hearing of infants is determining whether or not they hear that particular sound. Of course it's easy with adults and school age children, you simply have them press a button every time they hear a sound. Ellie is not so cooperative. One way to detect whether or not she heard the sound is to play it so loud that she flinches. Aside from being very irritating for Ellie and her parents this wouldn't provide any information about how well she hears low volume sounds.
What we need is a magical way of determining when she heard something. As usual when magic is required we turn to electronics. In this particular case we also need the help of some modern neurobiology. When a person hears something the ears send electrical impulses to the brain via the nervous system. As it turns out these impulses can be detected by sensors similar to the ones used for Ellie's EKG leads.
As you can hopefully see in the picture the sensors are placed on Ellie's forhead (black), jaw (green) and at the base of her neck (white). (Click on the image to get a better view.) These sensors will detect the impulses in Ellie's brain stem. Then she is fitted with around-ear earphones. Finally the computer program plays a series of clicking noises. The clicking noises are all the same volume (35 dB) but in different patterns. The computer knows the pattern sounds that it has played and so it knows roughly what to expect from Ellie's brain stem. The software then "cross-correlates" what it expects with what it measures to determine whether or not Ellie heard the clicks.
Now I know you're all thinking it, so I'll just say it: Technology is so cool!
As with any hearing test, the test equipment plays a sound for the subject to see if he/she will hear it. The central problem in testing the hearing of infants is determining whether or not they hear that particular sound. Of course it's easy with adults and school age children, you simply have them press a button every time they hear a sound. Ellie is not so cooperative. One way to detect whether or not she heard the sound is to play it so loud that she flinches. Aside from being very irritating for Ellie and her parents this wouldn't provide any information about how well she hears low volume sounds.
What we need is a magical way of determining when she heard something. As usual when magic is required we turn to electronics. In this particular case we also need the help of some modern neurobiology. When a person hears something the ears send electrical impulses to the brain via the nervous system. As it turns out these impulses can be detected by sensors similar to the ones used for Ellie's EKG leads.
As you can hopefully see in the picture the sensors are placed on Ellie's forhead (black), jaw (green) and at the base of her neck (white). (Click on the image to get a better view.) These sensors will detect the impulses in Ellie's brain stem. Then she is fitted with around-ear earphones. Finally the computer program plays a series of clicking noises. The clicking noises are all the same volume (35 dB) but in different patterns. The computer knows the pattern sounds that it has played and so it knows roughly what to expect from Ellie's brain stem. The software then "cross-correlates" what it expects with what it measures to determine whether or not Ellie heard the clicks.
Now I know you're all thinking it, so I'll just say it: Technology is so cool!
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Wow... that's intense.
ReplyDeleteWas she asleep during that?!? She looks awfully calm!