If you really need "it" tested, you can contact
these folks.
But a few issues that you will need to clarify first...
You mention STC measure specifically. This is a vague measure that is not necessarily a very useful practical measure as it fails to address some of the most problematic sources of practical sound transmission (specifically low frequency energy). One can meet STC levels and still be mired in what is an otherwise untenable subjective circumstance - so it pays to precisely define the nature of your perceived objection and then to identify and pursue a solution in a manner referencing legally defined standards that will more precisely address the specific problematic aspects to which you object.
Note also, that STC ratings are not generally used for the net large composite structures, but rather for the various constituent building 'components'. A fact that will be difficult to address if, say a wall meets the STC designation, but the flanking vector renders it nearly worthless. Yet another reason to holistically evaluate and to define the nature of the problem and to THEN devise a plan that satisfies the legal requirements as well as the acoustical standard of behavior... Assuming of course that you are not simply pursuing a Pyrrhic victory...
In other words, more precisely defining the problem determines what acoustical measure paired with what codified standard it is most appropriate to pursue. It makes little sense to pursue standard STC rating levels if, for instance, the preponderance of the problem is sub 100 Hz energy - behavior that is effectively outside the effective range of the STC measure...or if. for instance, the city codes do not reference STC standards... That would be a case were the wrong standard and tool has been chosen to reference a specific behavioral case, and you would hopefully want to chose a more appropriate standard that more adequately addresses the real nature of the problem as well as the legally enforceable standards.
You would do well to better define your criteria and pick the right tool for the job...
Additionally, related to this, since you reference the city, you had best find out precisely what the local codes and the specific noise criteria they reference. As if you will be n for a surprise if you reference other measures, while they may make for an utterly fascinating presentation, may very well be relegated to very enlightening, and moot point if they do not have legal standing as a result of codes failing to designate their objective legal applicability.
Specific site related noise is not difficult to evaluate, but the measure used for standards evaluation as well as the procedures to be used are defined and any investigation must be compliant with said best practices, as well as calibration, etc. Oft times NLA (noise level analysis) over time is a useful measure - again, dependent upon precedent and code. And it is your due diligence to discover these and to put together an effective and legally admissible strategy.
So, once the specific
appropriate terminology relating to the
specific defined quantifiable measures are identified, the rest is a pretty routine process. Unfortunately, 2/3 of the battle is determining the common language that all parties can reference in the discussion, thus allowing an objective determination of both the real objectively defined problem as well as enabling the establishment of an objectively verifiable solution - and hopefully one that is ultimately useful to your goals.
