Apps Preference is saved in wrong place

[QuickNick]

Good day, friends.

I'm wanting to build preference activity.
In the main activity I've wrote:

localPreferences = getSharedPreferences("My preferences", 0);
loopSound = localPreferences.getBoolean(getString(R.string.keyLoopSound), false);

I wrote in string.xml:

    <string name="preferenceTitle">My Tuner options</string>
    <string name="keyLoopSound">keyLoopSound</string>
    <string name="valueLoopSound">Loop sound</string>

In my_tuner.xml I've wrote:

<PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android" android:title="@string/preferenceTitle">
    <CheckBoxPreference android:key="@string/keyLoopSound" android:title="@string/valueLoopSound" />
</PreferenceScreen>

And in preference activity I've made:

addPreferencesFromResource(R.xml.my_tuner);

I've checked and unchecked checkbox, but its value is independent to the value in the main activity.

"loopSound" in main activity remains false despite of checked checkbox.
As I understand, my preference activity stores value in the another workspace, not in the "My preferences".

What's solution?