The article mentions increased levels of noise caused by human activity. It’s not just that we’re noisy, it appears that increasing levels of CO2 are acidifying the ocean, and — for reasons still not thoroughly understood — the decreasing pH decreases the ability of the water to absorb sound. See the article at NewScientist. Now theoretically this means that a whale’s call should be able to travel farther, counter-acting the first article’s assertion that “the effective range of blue whales’ calls is only about one-tenth of what it was before the era of engine-driven commercial shipping.” I suppose this depends on if there are areas of blue whale territory that are not affected by commercial shipping.