There could be numerous reasons for adverse reactions. Its sort of like asking, "Why do I have a headache?" One must assess the total situation. For example, one woman told me of an experience she had while shopping.  The sales person came to her with a large classic frosted bowl, put it next to her head and started to play it loudly. It instantly gave her a headache. This sales person was obviously not trained in the subtleties of using sound for healing. Placing a large bowl that close to the head without warning is definitely not a good technique! Some people report that the bowls make their hearing aids squeal. They may be using lower-priced models, or not have them set properly. I use two high quality hearing aids, and they are never a problem with the bowl sounds. 

To avoid avoid irritating people with crystal singing bowls consider: 

1)  What type of bowls are you using?  Classic Frosted (white) ones have one fundamental note, and not many overtones, so the sound can be harsher. Alchemy™ bowls have pure tones with many harmonic overtones that create a richly soothing effect. 

2)  How loud are you playing the bowls?  Try playing them softly, so that there is no buzzing. In my courses I teach subtle playing techniques. 

3) How sensitive is the person's nervous system? Some people have very sensitive nervous systems from birth.  They may also be extra sensitive at times due to noise pollution in their environment, illness, or stress. When I do individual sessions, I do a thorough assessment of the client's sensitivity levels. I communicate throughout the session, and gauge the "dose".   My students learn how to do this.

4)  What emotional associations are coming up?  Sometimes people burst into tears, releasing grief. Sometimes they suddenly feel connected with their True Self, and cry tears of joy. Some people don't easily talk about their feelings.  Instead they just report being uncomfortable or irritated. Its important to allow time to explore feelings, if the client is receptive to that. 

5)  Whats happening when discomfort arises in the body during a session? Sound penetrates the whole body and goes through the nervous system, acting like an acupuncture treatment. Stuck energy may cause discomfort. Usually it will release shortly, and the discomfort will go away. 

In short, there are many reasons crystal bowl sounds could be irritating. A trained sound therapist will take a holistic approach to finding solutions for each client.