Odd noise in Toyota Corlla

My '03 Corolla has developed a kind of low freqency wah/wah/wah/wah/wah noise that seems to increase in frequency as speed increases. I’ve had the tires re-balanced to no effect. Is this a simple and common problem or an automotive mystery?

It could be “cupping” of the tire treads or a wheel bearing.
How many miles on the car and tires?
Have you been getting the tires rotated?

tires have less than 10K miles; car has 42k. had to get new ones a year ago because they had gotten old and one developed a sidewall bump. no visible defects in tires. rotated every 5K. wheel bearing may be an issue; don’t know. any idea about how to determine? sounds more like front left but it’s more indefinite than clear. thanks for your comments