This question only has a localized relevance, since around the world different countries, and even states within those countries, can have different behaviour. Thus while Vitaly's answer is likely correct, then a large number of responses to this question will be That's not true where I am.
For example: (If Wikipedia is correct)
Audible signals, such as beeps, in order to help blind or
partially-sighted pedestrians; or a short recorded message, as in
Scotland, Hong Kong, Singapore and some parts of Canada (moderate to
large urban centres), the United States, including Michigan,
Massachusetts and Texas. In Japan, various electronic melodies are
played, often of traditional melancholic folk songs such as "Tōryanse"
or "Sakura". In Croatia and Sweden, beeps (or clicks) with long
intervals in-between signifying "don't walk" mode and beeps with very
short intervals signifying "walk" mode.
I think Croatia and Sweden have excellent ideas there and probably this is implemented elsewhere in the world too, maybe with slight variations from place to place - each country being at a slightly different stage or opinion of what's the best solution.
Perhaps the traditional songs might also be useful because you can tell how far through the song you are as you arrive, but it's a bit of a fluffy method with which to treat something serious like a pedestrian crossing...
In any case, the audible signal may not be the only method of determining state as in some areas, audible signals are switched off at night (or for some reason cannot be used in a given location) and in these cases tactile signals may be available - for example a small rotating cone on the underside of the button unit when the signal is at green to cross.
As a further indicator of the wide variation in implementation, a study into audible pedestrian signals in the US was made for the US Access Board (Bentzen & Tabor 1998 / Accessible Design for the Blind) and states:
The matrix entitled “Accessible Pedestrian Signals: Product Functional
Characteristics” on page 33 [shown below] shows the functional characteristics of
each product. Manufacturer information is given on page 34. All
products produce a sound, vibration, or both, during the walk
interval. Beyond this, there is great variation in the functional
characteristics of different products, with some providing information
throughout the signal cycle. A few devices have audio output that
varies, by message or repeat frequency, as the pedestrian cycle
changes from WALK to DON’T START to DON’T WALK