'Broagcast' - the /d/ sound in English

In comments, @Araucaria - Not here any more responded with:

There are several issues here. One is that the feature of the [d] that you cannot hear in these examples is called plosion. This is the effect you get when the articulators cause a blockage in the vocal tract, causing a build-up of high-pressure compressed air, and then suddenly come apart. With a /d/ you get plosion as the tongue comes away from the alveolar ridge (that little shelf behind your top teeth).

There are two possible reasons why you can't hear any plosion here. One is that when /d/ occurs before an /m/, the lips will likely close to make the [m], before the tongue comes away from the alveolar ridge for the release of the [d]. When the tongue does come away from the alveolar ridge the result is inaudible to a listener because it is masked by the lips being closed. The released air will escape through the nose instead of the mouth.

When we have a /d/ before a /g/, there will be a second closure for the [g] further back in the mouth at the velum before the [d]. This will reduce the air pressure behind the [d] and also reduce the volume of air that's released when the tongue leaves the alveolar ridge. Although it will be much quieter than the release of a regular [d], it may still be audible to a listener.

However, more likely than this, in both cases, is that there will be 'dealveolar assimilation'. The consonants made on the alveolar ridge are very unstable, especially [t, d, n]. They tend to change their place of articulation to match that of the following consonant. So a /t/ before a bilabial like /m/ will often become a /p/, a [d] will most often become a /b/ and [n] will become [m]. Behind a velar consonant [k] (as in broadcas these will become [k, g, ŋ] respectively. So what you're hearing is actually hibe my /haɪb mai/ and broagcast /brɔːgkɑ:st/. You can't hear any plosion in those realizations because the air behind the [b] is released nasally, and the air behind the [g] is not released but rather continues to be blocked behind the same alveolar closure which is used for the [k]. The vocal fold (vocal cord) vibration simply turns off during the same closure which is retained for the duration of the [g] and [k] segments. You can't hear any release, and thus any plosion, simply because there isn't any!

I don't hear the effect you are describing in 'hide my'.

However, 'broagcast' is a common type of assimilation /d/ → /g/. It happens because /k/ is the next sound that follows.

Another time this happens is in 'good girl', which sounds like 'gug girl' /gʊg gɜːl/. Notice that the /d/ changed into a /g/.

There's a good demonstration of this type of assimilation in this video: https://www.youtube.com/watch?v=sDDV01W20bo

In my London accent, I actually pronounce a glottal stop in this position (non-standard). This makes it have a 'swallowed' sound. /gʊʔ gɜːl/ (glottal stop in place of /d/).