diff --git a/src/fastmath.h b/src/fastmath.h
index f07f3c1..fe68f14 100644
--- a/src/fastmath.h
+++ b/src/fastmath.h
@@ -23,6 +23,51 @@
 #include <math.h>
 
 
+/**
+ * IEEE 754 Floating point representation
+ */
+
+#define LC3_IEEE754_SIGN_SHL   (31)
+#define LC3_IEEE754_SIGN_MASK  (1 << LC3_IEEE754_SIGN_SHL)
+
+#define LC3_IEEE754_EXP_SHL    (23)
+#define LC3_IEEE754_EXP_MASK   (0xff << LC3_IEEE754_EXP_SHL)
+#define LC3_IEEE754_EXP_BIAS   (127)
+
+
+/**
+ * Fast multiply floating-point number by integral power of 2
+ * x               Operand, finite number
+ * exp             Exponent such that 2^x is finite
+ * return          2^exp
+ */
+static inline float lc3_ldexpf(float _x, int exp) {
+    union { float f; uint32_t u; } x = { .f = _x };
+
+    if (x.u & LC3_IEEE754_EXP_MASK)
+        x.u += exp << LC3_IEEE754_EXP_SHL;
+
+    return x.f;
+}
+
+/**
+ * Fast convert floating-point number to fractional and integral components
+ * x               Operand, finite number
+ * exp             Return the exponent part
+ * return          The normalized fraction in [0.5:1[
+ */
+static inline float lc3_frexpf(float _x, int *exp) {
+    union { float f; uint32_t u; } x = { .f = _x };
+
+    int e = (x.u & LC3_IEEE754_EXP_MASK) >> LC3_IEEE754_EXP_SHL;
+    *exp = e - (LC3_IEEE754_EXP_BIAS - 1);
+
+    x.u = (x.u & ~LC3_IEEE754_EXP_MASK) |
+        ((LC3_IEEE754_EXP_BIAS - 1) << LC3_IEEE754_EXP_SHL);
+
+    return x.f;
+}
+
 /**
  * Fast 2^n approximation
  * x               Operand, range -8 to 8
@@ -69,7 +114,7 @@ static inline float lc3_log2f(float x)
     static const float c[] = {
         -1.29479677, 5.11769018, -8.42295281, 8.10557963, -3.50567360 };
 
-    x = frexpf(x, &e);
+    x = lc3_frexpf(x, &e);
 
     y = (    c[0]) * x;
     y = (y + c[1]) * x;
diff --git a/src/lc3.c b/src/lc3.c
index 9046abc..ac4427a 100644
--- a/src/lc3.c
+++ b/src/lc3.c
@@ -222,7 +222,7 @@ static void load_s24(
 
     for (int i = 0; i < ns; i++, pcm += stride) {
         xt[i] = *pcm >> 8;
-        xs[i] = ldexpf(*pcm, -8);
+        xs[i] = lc3_ldexpf(*pcm, -8);
     }
 }
 
@@ -249,7 +249,7 @@ static void load_s24_3le(
                      ((uint32_t)pcm[2] << 24)  ;
 
         xt[i] = in >> 16;
-        xs[i] = ldexpf(in, -16);
+        xs[i] = lc3_ldexpf(in, -16);
     }
 }
 
@@ -271,7 +271,7 @@ static void load_float(
     int ns = lc3_ns(dt, sr);
 
     for (int i = 0; i < ns; i++, pcm += stride) {
-        xs[i] = ldexpf(*pcm, 15);
+        xs[i] = lc3_ldexpf(*pcm, 15);
         xt[i] = LC3_SAT16((int32_t)xs[i]);
     }
 }
@@ -500,8 +500,8 @@ static void store_s24(
     int ns = lc3_ns(dt, sr);
 
     for ( ; ns > 0; ns--, xs++, pcm += stride) {
-        int32_t s = *xs >= 0 ? (int32_t)(ldexpf(*xs, 8) + 0.5f)
-                             : (int32_t)(ldexpf(*xs, 8) - 0.5f);
+        int32_t s = *xs >= 0 ? (int32_t)(lc3_ldexpf(*xs, 8) + 0.5f)
+                             : (int32_t)(lc3_ldexpf(*xs, 8) - 0.5f);
         *pcm = LC3_SAT24(s);
     }
 }
@@ -523,8 +523,8 @@ static void store_s24_3le(
     int ns = lc3_ns(dt, sr);
 
     for ( ; ns > 0; ns--, xs++, pcm += 3*stride) {
-        int32_t s = *xs >= 0 ? (int32_t)(ldexpf(*xs, 8) + 0.5f)
-                             : (int32_t)(ldexpf(*xs, 8) - 0.5f);
+        int32_t s = *xs >= 0 ? (int32_t)(lc3_ldexpf(*xs, 8) + 0.5f)
+                             : (int32_t)(lc3_ldexpf(*xs, 8) - 0.5f);
 
         s = LC3_SAT24(s);
         pcm[0] = (s >>  0) & 0xff;
@@ -550,7 +550,7 @@ static void store_float(
     int ns = lc3_ns(dt, sr);
 
     for ( ; ns > 0; ns--, xs++, pcm += stride) {
-        float s = ldexpf(*xs, -15);
+        float s = lc3_ldexpf(*xs, -15);
         *pcm = fminf(fmaxf(s, -1.f), 1.f);
     }
 }
diff --git a/src/spec.c b/src/spec.c
index bc4d5d4..25a28d4 100644
--- a/src/spec.c
+++ b/src/spec.c
@@ -135,7 +135,7 @@ LC3_HOT static int estimate_gain(
 
     float x_max = sqrtf(x2_max);
     float nf = lc3_hr(sr) ?
-        ldexpf(x_max, -reg_bits) * lc3_exp2f(-low_bits) : 0;
+        lc3_ldexpf(x_max, -reg_bits) * lc3_exp2f(-low_bits) : 0;
 
     for (int i = 0; i < n4; i++)
         e[i].q16 = lc3_db_q16(fmaxf(e[i].f + nf, 1e-10f));