We have a lot of "whistling" / whining, high pitched sounds from the plumbing, either after a flush, from any of 3 toilets, or sometimes just when running the water - even just cold water. The house is 50 years old, all copper supply pipes, but has NO pressure reducing valve. It had been an intermittment, infrequent problem, for some time, but has recently increased, and now occurs almost every time water is used. Seems to be worse when the water has not been recently used - e.g. after no water used for 15 minutes or more. Could this be too high water pressure, since it is so general? I have asked the city to send someone to check the pressure. Thanks in advance for any help / insight.

Your psi should be around 45. Check by attaching a pressure gauge to your garden spigot