However, those with ASD are sometimes also diagnosed with ADHD. Although they are different conditions, some of the symptoms can be intertwined, which it appears may be the case with your grandson. So I would start by trying out my tracks for ADHD. You can try those out for free on my YouTube channel and I’ve put them together in a playlist here: The corresponding MP3 versions for those tracks can be found on my site here: I hope that helps.
Gamma waves are the fastest of the brainwave frequencies (high frequency band of brainwave activity) which signifies the highest state of focus possible. They are associated with peak concentration and the brain’s optimal frequency for cognitive functioning – the 40 Hz frequency corresponds to a Schumann resonance band and many scientists, including Nobel Laureate Sir Francis Crick believe that it may be the key to the act of cognition. The Gamma state relates to simultaneous processing of information from different brain areas; information passes very rapidly.
From a brainwave entrainment effectiveness perspective, it’s my understanding that the response from isochronic tones stimulation starts to diminish over 30Hz and that 40Hz is about the limit for using them. So from what I’ve read on the topic a 100Hz beat wouldn’t work, probably because it’s too fast for the brain to process and synchronise with it.

Brainwaves, or neural oscillations, share the fundamental constituents with acoustic and optical waves, including frequency, amplitude and periodicity. Consequently, Huygens' discovery precipitated inquiry[citation needed] into whether or not the synchronous electrical activity of cortical neural ensembles might not only alter in response to external acoustic or optical stimuli but also entrain or synchronize their frequency to that of a specific stimulus.[16][17][18][19]
There are many ways to reduce tension and relax, but some are more effective than others. Some techniques are difficult to learn while others are challenging to practice. Others have negative consequences that almost outweigh their effectiveness or can create bigger problems. Here are ten stress relievers proven to be among the most effective for the amount of work and time involved. Most can be learned in the time it takes to read this page and will help you to feel more relaxed almost immediately. And even more exciting, the ​stress relief benefits will increase with regular practice. Try as many as you can—there's something here for everyone.
Meditation builds on deep breathing and takes it a step further. When you meditate, your brain enters an area of functioning that’s similar to sleep, but carries some added benefits you can’t achieve as well in any other state, and meditation actually allows you to build greater resilience toward stress over time. Also, the focus on the present moment keeps your mind from working overtime and increasing your stress levels, and from engaging in destructive mental habits such as ​​​rumination. Here's an article on different types of meditation to help you get started.
The group is loud and boisterous, cheering on their favorite team, jeering at the referees, complaining about bad calls, laughing at some of the terrible acting of the players as they writhe in agony on the ground in an attempt to get the referee to call a foul on another player, and then as soon as the call is made they spring to their feet and trot off, all memory of the agony of a moment before completely forgotten.

The activity of neurons generate electric currents; and the synchronous action of neural ensembles in the cerebral cortex, comprising large numbers of neurons, produce macroscopic oscillations. These phenomena can be monitored and graphically documented by an electroencephalogram (EEG). The electroencephalographic representations of those oscillations are typically denoted by the term 'brainwaves' in common parlance.[4][5]