How does sound affect the brain? The amygdala is a limbic brain center that has a role in responding to noise stress. When the amygdala is activated, chemical processes occur that can eventually lead to disease. Stress hormones are released into the body, and prepare us for a fight or flight, thereby causing changes in heart rate, blood pressure, cardiac output, blood glucose or lipid levels, sleep patterns, electrolytes, and more. So what is it about sound that annoys our brains? It can be one or more things. The sound's frequency, the duration, how long it lasts, the quantity, how many sounds we hear all at once, how often are repeated, and the volume. What do noise or unpleasant sounds do? They interfere with sleep, they interfere with concentration, they can affect our mood, they can cause damage to our hearing, they can cause physical pain, can cause an emotional reaction like anger, can cause chemical reactions in our brain and body that can lead to disease. Let's talk more about the elements of sound that affect us. It's the property of sound that determines pitch. Our hearing is the most sensitive in the frequency range of 2,000 to 5,000 hertz. There are some frequencies of sound that can be more disturbing than others. On October 4th of last year, we heard, or we're supposed to hear, a test of the emergency broadcasting system. You know how absolutely disturbing and annoying it is. I guess that's the point. The sound we heard was between 850 and 1050 hertz. The emergency alert isn't just an annoying frequency, it's also disturbingly loud. I'll talk about decibels or loudness later in this episode. Our hearing changes over time. Their frequencies of 40-year-old person can't hear that someone younger can. A healthier can hear a wide range of sounds from 20 hertz to 20,000 hertz. 17,400 hertz is a frequency that only teenagers can hear. 12,000 hertz is hard for anyone over 50 years of age to hear. 8,000 hertz can be easily heard by anyone with normal hearing. And here's some trivia. An emergency distress beacon, the kind used by ships and planes, transmits at a frequency of 406 megahertz because that's the frequency satellites can pick up in the event of a distress activation. Duration, how long it lasts. When I hear a particularly disturbing sound and it lasts for a while, I can feel the energy travel up the nerves in my arms and to my ears, which then start to hurt. It's as if my eardrums are screaming stop.