Drag the right side control point down to the bottom.

The result is that regardless of what the player’s health is, 200 dB of volume will be subtracted from the heartbeat's normal playback level. In most cases, anymore than 80 dB of volume being subtracted would prevent the sound from being heard, so it’s safe to say that the heartbeat won’t be heard at all. You’ll need to make another adjustment.

We don’t want the heartbeat to be heard until the player's health falls below 50, so you’ll create a curve to accommodate this, which can easily be done by adding more control points.

Double-click the curve at around the 50 value to create a new control point.

A new control point is created.

Click the far-left control point, then type 0 into the Y: coordinate, and press Enter.

You can zoom in on sections of the curve by using the plus and minus symbols in lower right corner of the graph. The icon in between the plus and minus symbol resets the graph view to display the entire curve. You can also use Z+click-drag to zoom in; or use Ctrl+mouse wheel to zoom in and out vertically and Ctrl+Shift+mouse wheel to zoom in and out horizontally. See the Keyboard Shortcuts and Commands available from the Wwise Project menu.

Now the heartbeat’s volume won’t begin to increase until the player’s health falls below 50. Sometimes linear transitions, especially for volume, don’t create the smooth transitions we’re looking for, so further modifications to the curve are necessary. This can be done by creating a lot more control points, or more complex lines can be created quickly by using various preset curve styles. In this case, you’ll modify the curve to more rapidly raise the volume once the health falls below 50, and make only a gradual increase in the heartbeat’s volume as the player’s health falls closer to 0.

Right-click the curve anywhere to the right of the control point you just moved and choose Exponential (Base 3).

It’s very difficult to know exactly how to set the curve without auditioning how it will sound by simulating a change in the Game Parameter while listening to its effect on the property you’re adjusting. To do this, simply play the Heartbeat object and move the PlayerHealth Game Parameter Cursor at the top of the graph to the left or right.

Play the Heartbeat and drag the PlayerHealth parameter cursor left and right to hear the effect of the Game Parameter on the Heartbeat object.

Besides increasing the overall volume of the heartbeat, another way to gradually make the player aware of the heartbeat is to open a low-pass filter. A low-pass filter only lets sounds below a set frequency pass through. Setting a low-pass filter so that only the lowest frequencies of the sound can be heard makes it sound muffled, which is a great way for the player to start to hear the heartbeat. Gradually opening the Low- pass filter will make the heartbeat sound more pronounced and obvious. Since Wwise lets you map a single Game Parameter to multiple properties, you’ll add a low-pass filter curve in addition to the volume curve you just created.

Click the next available [>>] selector to map a second property, the Voice Low-pass Filter, to the PlayerHealth Game Parameter.

You now see two lines. Red lines indicate a volume curve, while blue represents a filter curve.

The Low-pass filter property value can range from 0-100. Think of it as a percentage that indicates what percentage of frequencies will be filtered away, starting at the top of the frequency spectrum. In other words, a value of 20 means the top 20 percent of the audible frequency spectrum will be filtered off making the sound seem not quite as bright or clear. Since the default value is 0, it means that currently there is no change to the audio, and all of the frequencies in the sound can be heard.

	You can find an in-depth article related to low-pass filter values at Associating Low-pass and High-pass Filter Values with their Corresponding Cutoff Frequencies

Like the volume curve you created, you’ll start with all of the frequencies being filtered away and then, once you get below a certain point, gradually open the filter until all of the frequencies can be heard.

Raise the right-side control point to the top and add a second control point near the 60 value. Raise this new control point to the top.

Experiment by adjusting the PlayerHealth parameter in the graph view while you listen to the heartbeat.