Julie has a problem I'm sure a lot of you can relate to!
My 15-month-old son will squeal at such a pitch as to cause terrible pain in our eardrums. He will squeal when he is frustrated, not getting his own way, having to sit in one spot too long (eg. Out for dinner, or in the stroller shopping)…normal toddler issues. What can we do to stop this? Should we ignore it and cause the general public to also deal with ear pain? Or is it time to start some discipline with timeouts?
This is a tremendously common toddler behaviour, particuarly at this age, when language is generally so limited. It is a way to express their feelings, and it's generally hugely effective at getting what they want. For the toddler, it's a win-win. Not so much for the parents and any innocent bystanders!
What to do?
First, whenever possible, avoid the squealing by dealing with the situation before it gets to that point. (I'm quite sure you already do this, but I can't skip it and have everyone assuming I don't do this first, too!) Take the tot from the high chair as soon as he's done; leave the mall when he gets restless. Bring toys to distract and snacks to keep the blood sugar stable.
If squealing starts, speaking simply and firmly, identify the problem, and give the child a positive option. "Suzie! Too loud. You want down? Use your quiet voice. Quiet voice." When you say "quiet voice", say it quietly. Model a quiet voice. You may have to put your lips right to the child's ear in order to be heard over the racket she's making!
Sometimes, particularly when we're in public, I will point out some distraction in a whisper in the child's ear. ("Oh! Freddie! Look at that fire truck! See the fire truck? It has ladders and hoses. Maybe the firemen are going to a fire. Do you think the truck is going to a fire?") Often very effective, and a quick fix for public squealing.
As far as misbehaviour in public: At home you will have to put up with yowls of protest as you teach a new behaviour or raise your expectations of your child. However, I believe it is inconsiderate to inflict this on the surrounding public. If the child isn't calm in short order, I always leave. Don't worry: this doesn't mean that you're training your child to misbehave in public: the real training for good behaviour anywhere happens at home. Innocent bystanders do not need to spend 20 minutes caught in the crossfire of someone else's battle. (I'm aware that this is a multi-layered subject of a much longer post, but that's my working principle in these situations.)
Third, and the most important, a principle applicable to almost any behaviour you wish to eliminate: don't reward the behaviour! Whatever the child wants to achieve by the squealing, make sure it doesn't happen! For example, if she's squealing for attention, put your hands over your ears and walk away. Remove your attention.
(It is not necessary to say anything to the child. The most you need say is, "Oh! Too loud!" with an unhappy frown. Then leave, hands over ears. Body language will speak as well as words. You can prevent him/her following you by having a baby gate up. You can either step past the gate, leaving the child behind, or you may put the child on the other side of the gate. But do not be bathing the child in words and explanations as you do this - words and explanations, even scoldings, are attention.)
Another example, with a couple more options: Baby wants down from the high chair.
Be sensitive to whatever (non-squealing) cues she's giving you; use words to confirm her cues. "You want down? All right! I can get you down!"
If she squeals, offer an alternative to squealing. Words if she can speak, and/or signals if she can't. "You want down from the high chair? Say 'down, please'!" As you say 'down, please', you rap on the chair's tray with both hands. Take your baby's hands and smack them on the tray as you repeat "Down, please! Down, please!" This sort of thing can very quickly become a game.
A variation of the above is to add the remove-attention tactic. "I can't help you when you yell at me. No yelling. I'll help you when you're quiet." Then you very deliberately turn your back on your child. Wait fifteen seconds or so, then turn around and try with the alternate again. ("Say 'Down, please!''' and slap the tray with baby's hands.)
As baby gets the idea, raise the bar. It shouldn't be too long - two or three weeks - before baby understands what "No yelling. Quiet voice," means, and that it's more effective to rap on the tray than squeal. Not every time, but you'll see substantive progress.
And if you're discouraged by slow progress, be assured that this behaviour is generally 'just a phase', and that it will fade as their vocabulary improves. It's good to make the point now, though, lest you find yourself, in another few months, being screeched at -- in actual words!